Apple has posted an article suggesting using CVDisplayLink instead of NSTimer to drive your render loop...

http://developer.apple.com/qa/qa2004/qa1385.html

I've tried the display link route in the past. It works, but does not seem to improve performance over the 1k timer with vbl synch (i.e. it still stutters intermittently). It's okay though, I think the display link is a good idea in theory and is worth using. Glad to see they updated that technote.