Nothing's game-breaking wrong with them, they don't crash, and even the features that 'don't work' have some functionality. Here's some things I've noticed: Assassin's blend doesn't work as advertised. It does, however, allow you to hide anywhere you could normally hide once the guards are onto you, even if they can still see you. On the DirectX 10 version, the add time button doesn't work (Says 'activated', but no more time shows up). Simple solution is to go back to nine, complete the part that needs it and switch back.
That's all I have noticed, but these don't really need fixing since there are ways to work around them (and you have more important things to be doing), just letting you know here. Long live Cheathappens!
All times are (GMT -08:00) Pacific Time (US & Canada). Current time is 9:13:50 AM