A friend has an Android phone, and the interface is very good. The App store doesn't have as many applications as the iPhone, but the overall quality is a bit better, since Android users seem to know if an application is really worth getting or not.
Applications like Google Maps, Google Sky Map, Layar are free and really awesome. Paid applications like yxflash to play DivX movies are also welcome.
If you're a heavy Google user, you'll of course get the best Gmail, Google Calendar, etc. support.
The performance is usually degraded when companies like HTC and LG add an extra shell on top of Android, so you are advised to shut them down, and use the normal Android interface.
Another problem is getting the latest Android version. A lot of people that bought the first Android phone (G1) can't upgrade to version 2.1, because the manufacturer hasn't released an upgrade package. You should definitely look at that.
Once my provider subscription ends, and I can renew it if I choose a new phone, I'm thinking about getting an Android phone myself.