HTC Hero. It is the best phone I've ever owned. I'm in simple words amazed by this device. May be its cause I jumped generations of phones, my previous was a shameful Motorola Rokr (even Steve Jobs got pissed at it :P)
You'll find all sorts of superficial and in-depth reviews about this device. But to summarize it has good hardware, has a great UI(HTC Sense), a stable platform(Android) and a great app store (off-course nothing beats Apple's app store). I was so much sold, I decided to switch to Sprint from AT&T for that, which can now be regarded as a wise move considering Sprint's network and plans.
Recently I wanted couple of things, a GPS, a pocket camera, a portable music player and a new phone, and this sweet device does it all. Why not iPhone you would ask, wouldn't you?
Well, my hatred of iTunes ranks first in the reasons I have. I don't use iTunes even on my Mac, simply don't like it. Secondly, background apps. This phone(Android in general) has background apps that can do magic, like put the phone on vibrate when at work, turn wifi on at home, mute notification sounds in sleep time. And the not so magical but essential things like listen to internet streams while doing other stuff, have notifications for tweets/facebook/whatever-you-want, chat without getting logged off on switching the app, and use a GPS/maps app while using other apps. Thirdly, iPhone is just not cool. There, I said it.
There are fourth, fifth and some more reasons, you may have a look at the fantastic Droid ad to get a hold.