[quote name='token2k6']the 'broken' isn't that bad if you think ahead. Basically the issue comes in with completing the game, then going back to certain levels to collect the rest of the items for the achievements. Supposedly, when loading certain levels, the game will just freeze and may corrupt the save file. So, just grab all the items on your first play through, or on another, without completing it first, or make sure to grab all of the ones in the levels mentioned for the glitch. There is an achievement for completing under 12 hours, collecting everything may make this close. So do one play through under 12 hours on Uber and at the end you will get like 5 achievements (stackable difficulty) and then start a fresh game and go after collecting everything and mop up.
EDIT: buddy of mine who has completed the game, and is working on going back to find items. He swears he's loaded every level and no glitch, so this may be random as well...[/QUOTE]
The save game mechanism was not well designed. On the PS3 they use one save file which inside contains all the checkpoint saves. By using one large file there is a per-file size limit and after passing a certain level, you can't go back to those levels.
Aside from that, its a fun game. Not as good as the previous installment, RtCW though.