My 17-55 EF-S f/2.8 IS USM is only three months old, I bought it at Samy's camera. I just got a Canon 70-300 EF f/4-5.6 IS USM two weeks ago, and it was so noisy I thought something was wrong with it. I was so concerned that to test it before calling Canon CS I mounted my 28-135 and you could kind of hear it if you put your ear along side the lens barrel, but not from behind the view finder. When I mounted the 17-55, I could only hear it if I put my ear directly against the barrel of the lens and engaged the IS. I cant hear the IS at all from behind the view finder. After talkling to the people at Samy's Camera, and searching the internet it seems like occasionally the 70-300, 75-300, and 70-200 can be noisy. I compared my 17-55 to my bro-n-laws 16-35 L f/2.8 and what little IS noise there is, is the same as my lens. I have a 40d, which doesn't have video capability.
Interesting comment from Rick about it being whisper quiet. Have they changed the IS system?