On my iphone 3G I checked the stats just before upgrading to iphone 4. I use pandora internet a lot, surf the web tons, download apps, upload pictures to facebook, etc. I don't watch a lot of youtube or other videos.

I used about 6 gigs in 15 months. My wife used about 2 gigs in the same 15 months. Any time I am at the house i am pulling wifi. At work I leave it on 3G because the network is pretty restrictive.

-David