I usually go to Engadget for all my tech news, and low and behold they've posted a GREAT review of the iPhone 3G...
I've yet to purchase one yet, only because the AT&T store has been sold out for 2 days now, and I really don't feel like camping out for it when I already own an iPhone that works perfectly fine... I'll just wait til Monday, hopefully the crowds will have died down by then.
http://www.engadget.com/2008/07/11/iphone-3g-review/