Fergregoire94, I think at this point the biggest issue a new Linux user has with Linux as far as accessibility goes is simply his or her unfamiliarity with the operating system, screen reader, and the graphical desktop he or she may be using. It is those kinds of things that makes or breaks a person's end user experience with Linux.
For example, in your post above you mentioned having problems reading certain help topics in Gnome or Unity. What probably was never explained to you in order to read a help topic in help you first have to enable carrot browsing with f7. If you don't do that the help system is going to appear inaccessible and problematic for a screen reader user. Its a classic case of something being accessible, but the end user not knowing what to do to use the technology. So since you didn't know what to do to make the help browser accessible you assumed it wasn't.
The more I spend time with new Linux users, those who come from Windows, I find lack of knowledge accounts for the better part of access issues. I'm not saying there aren't any legitimate access issues, there certainly are, but often times there is a quick or simple workaround for an access issue that the end user simply didn't know about because they assumed access should work one way and it turns out they needed to do something else instead. The fact of the matter is Linux requires more of the end user to get it up and running smoothly and if a person lacks those skills or the experience to do that he or she is in for a negative experience more or less because of their lack of know-how.
That said, there definitely are some legitimate access issues on Linux that need to be dealt with. These issues certainly can and do lead to an a less that satisfactory experience for some users, and it is something that needs to be considered weather the access issue is a deal breaker for the end user or not.
For example, on the stock Ubuntu 14 distribution it comes with the Unity desktop. Unity is 80% to 90% accessible. However, there are times where something such as the Dash doesn't work well with Orca yet. I personally don't need it so do without using the Dash, but someone else might want access to that feature of the desktop and find it is an unsatisfactory experience because of it.
However, here is the nice thing about Linux Windows users consistently overlook time and again. You aren't stuck with just one graphical user interface. If Unity doesn't work for you there are other options. There is the Gnome desktop which is becoming fairly accessible these days, and is probably the best end user experience for a blind user right now. there is also Mate which is a continuation of the old Gnome 2.x desktop which is also a reasonable option. Linux is all about customizability and its up to the end user to find the customization that works best for him or her. The problem is a new user doesn't know where to begin or what to do to get Linux to work the way he or she wants. that is where access really breaks down because there is no access for dummies type book or tutorial that lays it all out for a new user.
I'll simply reaffirm what you said above. Yes, it does require a bit of effort to get working properly, but once a person gets up and running with a decent distribution, running an accessible desktop, there isn't a lot of need to run windows unless someone absolutely wants to. I've been able to do most of what I want to do in Linux with reasonable access for about three or four years, and while it requires some tweaking on my part I was willing to put the time and effort into learning about how to get the most out of the operating system and apps.
I'll be the first to say my end user experience hasn't been perfect or as good as I personally would like. There are a number of cases I could mention here where access is not as good as it could be or as good as it should be. Firefox and thunderbird are a couple of cases in point. However, I put up with the access issues, because over all I like the operating system, and am willing to compromise on some issues to get things I want from the OS. Someone else like yourself coming from a Windows background may not have my reasons for using the OS and would find the access issues unsatisfactory and give up on Linux because you have different expectations and uses for the software.
Sincerely,
Thomas Ward
USA Games Interactive
http://www.usagamesinteractive.com