A big issue that is getting some press has resulting from new products like XNA Game Studio and the questions are arising about how to make things like the garbage collector deterministic in managed code. If code in a critical game loop is stalled, for garbage collection, the results would seem to be very bad (stutter, dropped frames, oh my!). Luckily, the CF team that worked on the XNA Framework has taken this into account (they got our backs sometimes ;)). Listed below are 2 articles detailing some of these optimizations. Good Stuff!!!!
Managed Code Performance Part 1
Managed Code Performance Part 2