Samsung keyboard is nice and snappy. The only thing I don't like about it is the fact that you can't adjust the delay required for a long press of a key to register. At least, not that I've found. Other than that, it's great, and predictive text works well though I usually have it turned off.

so I finally got the decaTXT. 
this is a bit of a long, thorough review (also posted on amazon)

Shopping experience: As amazon did not have international shipping available, I had to contact the seller via e-mail to arrange buying details and who very kindly shipped it to me. I agree with everyone on the excellent customer service they have.

so this keyboard... had me thinking for a while.
I am a blind android cellphone user and wanted something that allowed me to type faster and make less mistakes. Dictation normally did the trick (and still does) but touch screen typing was very annoying, although autocorrection saved me often. I have been using it for a couple of weeks, and even though there was some practice involved, the system is interesting as it functions similar to braille, where you have to press combinations of keys or dots to make letters. Only time would tell if speed really increases as opposed to using the onscreen keyboard, and if so I will definitely update, but some words are easier to grasp and I believe speed will increase.
An attempt for a  physical description is in order, however.

This device is rather small. It has a rectangular shape, and its almost but not quite as long and as wide as a credit card. Its about one half inch thick, so think of a stack of about 15 cards tightly put together or a thumb finger.
The long side edges are rough,probably using sandpaper so you can have a firm grip of using it one handed (more of this in a bit)
One of the sort edges has two square raised plastic keys that protrude slightly plus a small protruding edge underneath, and the other one just opposite that has the micro USB charging port without any additional tactile difference. The cable should be inserted with the dots pointing upwards or in the same direction of the plastic keys. On top of the device on a smaller thin rectangular platform are 4 rows of square shaped, raised plastic keys that should be just wide and spaced apart enough to accommodate the pad of your fingertips. The side opposite of that, has some curious air bumps, bubbles? that cover the screw holes, and a sticker with printed instructions but nothing else.
With this being said, the device should be positioned so that the short edge of the rectangle that contains the plastic keys is facing you, and the top of the device where the rest of the keys are is facing up. Thus the A key where you should put your right index, is the very first one on top on the right row. Beside that one is the G key where your left index should go. The two thumb keys that are facing you are the E key on the right, and the F key on the left. You should, and if you really can, place the two thumbs side by side on those keys that are on the edge facing you, and all the other fingers should rest on the other keys on top of the device. This is not to be used on a table, otherwise it will be rather uncomfortable and not at all ergonomic. In fact, if you really want to use both to type you need to make your hands almost into fists, which is a bit straining, then again one of the major features of this is one handed typing.
So now,  with this in mind you can follow the manual from the website all the way through, which is sometimes out of order in some paragraphs, especially the introductory ones which confuses things.

Regarding one handed typing: You should definitely use the hand you use most when starting. Using the other one mirrors the orientation aspect of the keyboard, but its totally usable with either hand. As the manual describes, the thumb keys should point to the opposite side of whichever hand you are using,  and the device is to be tilted to the side and held so that one rough edge is placed against your leg or something and the other one touches your palm, so its another sort of fist again with the palm of your hand opened, but this one is more ergonomic. The rows of keys that were on the top now face away from you and form short columns of two, and the thumb keys should be well, next to your thumb.

The keys: They are standard plastic-type keys which feel OK and give a good sense of awareness. However, pressing for example, the ring finger shifts or the two pinky shifts as described in the manual  keys plus something else is a bit cumbersome at times, especially when using just one hand it becomes a bit painful sometimes.

Bluetooth: Pairing works a charm. However,  frequent and intermittent (as you would normally use bluetooth based things) usage of the device needs patience. As modern android lets you see when devices are connected or not from the notifications, you can tap on them to connect and disconnect. I find that you have to disconnect when you don't want to use the keyboard anymore, and then reconnect twice or sometimes three times for the keyboard to work. Somewhat buggy but the seller tells me this is due to a power chip that isn't as good. Bluetooth is very stable during a session, long or short so that's good.

Portability: this is good. You can carry it anywhere. The not so good aspect is that keys may get sometimes easily pressed so some sort of protective hard case is recommended. (more on power in a bit)

Functionality: As with anything bluetooth, there will be some lag though here it was very little. Your screen reader will announce what you have typed, as per your configuration. You should use that to your advantage when you are learning the layout, otherwise you can turn that off and have characters read only when you use the onscreen keyboard. I also recommend finding an app called External Keyboard Helper which really expands the functionality for any physical keyboard on android and even lets you create custom mappings, it will just set you back two very well worth dollars, which if I assume you have bought this keyboard is because you can easily buy the app as well.

Internationalization: When connected at least to android, This will show as a physical keyboard that complements the onscreen keyboard you are currently using (I use google's keyboard called G board because it has automatic autocorrection announcements and other accessibility goodness). This makes up for an interesting or problematic (depending how you look at it) keyboard layout internationalization/standardization case.
For example: When using any pc keyboard int he world, if you happen to switch the system configuration to layout to Spanish, pressing the key just to the right of the letter L will produce the letter ñ. Exactly the same happens with the decaTXT. The manual states that you can produce a semicolon using the 4+9 key combination. In this case it produces an ñ character, because the key that is right next to the L in the English keyboard layout is indeed semicolon, but it changes according to the language and keyboard layout you have, so keep this in mind. On the flip side, this renders the instructions for producing international characters somewhat obsolete. You could just switch system keyboard layouts on your device and use that to your advantage which is actually much easier in my opinion than having to issue three or more separate keystrokes just for one simple letter. The most daunting downside to this is that you will have to figure this on your own or by referencing and comparing your language with the american english layout all the time and thus the acronyms and memory aids just confuse character generation even more. Still, this outweighs the negative aspect of it. Lamentably, Gboard has very broken support for typing an accent and then a letter, so again External Keyboard Helper comes to the rescue, or any other soft touch type keyboard.

Software usability during typing: This was the part I actually liked the most. This will act just the same as if you were using the screen to touch type. Which means that depending on the android keyboard you use or have installed, the same features will be available and work. In this case, as I was typing the phone was predicting and suggesting words, so I did not even have to type the words completely before they would be guessed, and so I ended up remapping the space key with the f key. Also, autocorrection normally puts the accents and other language specific things in for you so its another win and one less negative internationalization aspect to consider. You can use it anywhere too for executing all sort of undocumented commands on android like windows key plus g, which opens up gmail and so on. Again, External Keyboard Helper greatly enhances all of this and more.

Power and charging: I have found that from 0 to 100 percent no more than three hours is necessary (plugging this with the included cable into a regular USB 2.0 port on a computer)..  I found out, perhaps the hard way, that the device stays on all of the time, despite the user guide telling you that you need to press a button to wake the device and then pair it. This is certainly most bewildering, and there is actually no way to save power. If you have the device synced, you can connect to it. It will give an error for the first time and then if you try reconnecting to it, it will connect and vibrate three times. Sometimes you will need to disconnect and reconnect yet again for it to work. So there is not a way to control the power other than charging the device fully, and then waiting for it to discharge fully, which takes around 6 days with a typical two hours average use per day (not sure if using or having it connected all the time will discharge it faster though). It will not time out and auto power off, or anything of the sort. This explains why mine came totally discharged when it arrived.

All in all this is a nice idea, I am liking it so far despite it being bluetooth buggy and not as comfortable, keys are somewhat cramped but that is due to its rather small size. Strong points are the software usability and  how discrete, lightweight and practical it is.
So, its four stars due to bluetooth being buggy and lack of some more precise, practical  instructions and some features that could have been more obvious, like power control or at least a way to know when the device shuts down and also a way to retain the only one setting you can make, so you wouldn't have to press the combination to swap space with F every single time you turn it on.