The big question always is, did you listen to music or not. If so, you're almost inflating your result by the time you used the ipod.
So, that being said, today I used the phone heavily, lots of web surfing via both wifi and 3G, lots of speedtest tests on 3g, which must be tough on the battery, about 30 min 3G calls, some email and sending large pics, but, no ipod, and I hit the 50% mark at exactly 3.5 hours of pretty hard usage. It'll be interesting to see how accurate the battery indicator is, and if that number doubles or not, I did run it to zero last night, then fully charged, so it should be accurate.
Whenever I used my 3Gs this hard, with no ipod, I was lucky to get 5 hours, so, it seems I'm getting 2 hours or so more use from the 4. Not bad.
On a more normal day however, I'd listen to an hour or 2 of music, which would add approx. another 1-2 hours to my time and get me close to 8.5 hours. Obviously that's pretty decent for what is essentially a tiny laptop that also makes calls.
Other issues aside, they sure did a good job of packing the phone with features, more power, much better display, while actually increasing battery life.
