OK, time t chime in...
I think there have been alot of good points made here.
True that things can come up in the middle of developing games. But, I can understand why people are mad about it. How many times has it said in some form or another that the game will be available by a certain date? I think there's been 3 or 4 times when I've thought the game would come out, only to find that it had been delayed again. To be fair, though, it seems like from posts I've read that sometimes James has explained on email lists why it is taking a bit longer.
I think another reason people are upset is that they're wanting a new game to play. The same thing happens in the mainstream gaming world, too. you know there's not a "quality" new game on the way when on alot of the current game system boards on GameFAQs, you see topics like "what color is your gba?" "What game should I get?" "What game is in your PS2/Xbox/GameCube/GBA right now?" and my personal favorite "why Nintendo/Sony/MS will win next gen." or something to that affect. LOL Good ol gameFAQs.
The difference is, that with audio games there are so few games to choose from, and alot of them to me at least, seem extremely similar. I.E. Alien Outback/Troopanum 2/Dark Destroyer. They're all Space Invaders clones. Every once in awhile I'll try and beat my score on AO, but that can get boring real fast sometimes.
If it could work, it would be cool to have all demos only be limited by time. Then it'd be just like renting a game for a mainstream game system. I don't think that is realistic for PC games, though, because you would only be able to play the game once until the time limit ran out. LOL I actually tried to download Troopanum 2 more than once. IMO that is a good example of a shooting game done right. Good ol BSCGames.