Features get cut all time, but usually not after so many people have played them. I guess that's the big part of why everyone is upset, but the level of disappointment is a little silly.
The discs were a very cool feature, for sure. But they were secondary to the shot geometry on the game, which was already a huge success. After playing it a bunch at TPF, I never really felt the impact of the 3 disc setup, but thought it was neat. With so much already happening in the game, it's a disappointing, but hardly disastrous omission.
For people who just look at their games, and let's not pretend that Pinside isn't full of those types, the change is probably a big blow. For people that will care about reliability first, it's probably a take some good with the bad sort of announcement.
Reliability should always be king. It's one of the main reasons I don't enjoy Star Wars or The Hobbit. I rarely find one that's reliable top to bottom.