I mentioned previously my experiences with an iPhone; in essence, I hated it. I had played around with Android on a Motorola Milestone, and thought that was pretty awesome - although the Milestone had its own issues. I got my hands on a Google Nexus One - fortuitously it appears, as Google is no longer selling them.
Its only been two days, but this is, without a doubt, the best phone I've ever used.
Mine is already rooted (because I want to run market-enabler, the tool that allows me to buy apps outside of the US), running Froyo, aka Android 2.2. Major highlights for me include the ability to run Flash and the fact that its so much faster than Eclair, aka 2.1. The battery life for a phone with this type of screen isn't bad (it lasts me one full business day), but thats not enough, so I have ordered an extended battery.