I've tried both Exchange and Google calendar sync, and neither is fully reliable for me. Both sync most events over, but some events don't sync in one direction or the other, though they may show up as light gray bars with no text in the Pre calendar. I've got a few other, more minor problems, but this is the one thing that really undercuts the Pre's usefulness for me.

I know there are other users who do have these problems. Are there users who don't? If you make heavy use of calendar sync with no problems, that might help in tracking down the problems some of us are having.