I have the 2.3 i7 with anti glare screen. I have been writing an econ research paper on it with probably 20 tabs open on Chrome over 2 windows, two documents open on word, large excel spreadsheet, outlook going, and itunes. It is dead silent and doesn't even feel warm.
Right at this moment I am transferring over 60 gbs of music, copying a dvd using handbrake and itunes. The fans are going but they're not that loud, kind of like a louder hum if that makes sense.
Edit: I just finished the handbrake and now it is back to being dead silent and its cooled down to a moderate warmness.