I've had an iPhone since the first one came out a few years ago and I have loved every one I've had since then. I used to find myself buying a new "cool" phone and getting sick of it in about a year tops, that has never happened with my iPhone yet!
My fiance got his iPhone 4 the day they came out and it is his first iPhone and he loves it. I've played with it and I have to say there are a lot of things about the iPhone 4 that are better than my 3G. For starters, it is way faster. We connected to wifi last night and opened the same webpage at the same time, in theory it should load at similar speeds because we were using the same connection, but his loaded in half the time mine did. The display is amazingly clear and it takes great photo and video. I would recommend anyone to get an iPhone, I highly doubt you will be disappointed.
Edit: I forgot to mention the facetime feature and the forward facing camera. Its awesommmee!We have several friends with iPhone 4's now and we can do video calls with them. Its just a very cool feature. Also the antenna issue is fixed by simply putting a case on your phone...which everyone should have on anyways (not saying that they didnt make a stupid mistake, but everyone should have a case)