Yeah, mandatory installs suck ass. Being forced to wait a few minutes in order to play the damn game is ridiculous. Seriously, we're not on PC's here.
On the other hand, it's not exactly all rosey on the 360 side. I end up doing the optional install whenever I can because the benefits (to me) are practically mandatory... the loading times and noise on the console can be pretty ridiculous. Worst of all, thanks to the proprietary BS I'm stuck with a 14gb HD. That's only enough room for 2 DVD's, can't even fit a 3 disc RPG on it.
Now, it's not the end of the world (don't bring up the Wii's problems, I'm aware), but it's still an issue. One I hope is fixed on the next set of consoles...
@nordlead: The patches for games I play on the PC often come with content or fix balance issues. I think it's debatable whether that's a good thing or not, just two different models really. I can't imagine playing some games without the developers' continued support (even when unincluding MMORPG's, which require it).