There's a ton of news on the net about the iPhone 4 antenna concerns but the jury is mostly still out on that. For my own limited testing, within my home office I no longer get reliable coverage with the iPhone 4 where I did reliably with the 3G. Thats a concern. Full disclosure, i'm a righty.
Other than that, with the faster phone i'm enjoying the new folders and overall phone a lot more. One thing i've noticed missing in Apple's advertising is that with about 77% of people buying the new iPhone 4 being upgraders, i'm sure a large percentage of them are like me, iPhone 3G users. They've been touting the new iPhone 4/iOS features over what the 3GS had but they're missing the fact that many of us never experienced those. There's all sorts of new stuff in there not covered by recent press thats new and wonderful to me like voice dialing, compass, etc. Some of the apps also use this like AroundMe where if you use it in landscape mode uses the compass to do a virtual reality like thing showing how far away places are which is really cool:
Its unlike Apple to miss a marketing opportunity and with this antenna business they could use some extra help.
Meanwhile I got my phone back and i'm in love again. I just hope they don't break it once more when iOS5 comes out...