I have this lens and it does make a noise - you can hear it compensating if you move it - and starting up you hear the gyro's

Out on a trip to Kew Gardens today. I spent most of it using my 100mm macro lens which is as quiet as a mouse but then thought about this thread so gave my 24-105mm lens a test. My lens is also as quiet as a mouse. I wonder if the shop got a bad batch?

Andrew

Mine is very quiet also , my 70-200 2.8L IS is a little noisy though...

Well maybe it depends on what you class as noisy compared to the others on the thread? 

Unless the noise is a problem in itself (ie you're taking weddings and it sounds like a washing machine) I'd keep the recipt and see what happens.  If it is a mechanical problem I'm sure that it will let itself know the more that you use it. 

Perhaps fire an email or letter off to Canon so they have it on record, in case it fails just outside of the warranty.