I'm a little OCD, and am usually the first to notice the smallest defect, but so far I'm very happy with it. The display is amazing, noticeable speed bump both in processing and Internet, no prox. sensor issue, and no reception issues I can detect, and I've looked. In fact today I had lunch at a little place I often go to, I have never once been able to get data/Internet in there, today with the 4, in literally the same chair I always sit in, I was able to surf the web, not 100% speed, but decent, where with my 3GS in the same spot that never once happened.
My 4 also tends to get faster overall 3g speeds in my house according to the speedtest app.
If I'm being very picky, I feel like my battery isn't quite as good as some, but, I think many of the people posting usage of 8-10 hours on one charge might have an inflated number due to iPod use.
I know if I listen to a lot of music, I can add several hours to my usage times.
My typical usage on one charge is about 6:45 and 15 hours standby, but that's with NO iPod, and pretty hard use.