I have a Nexus One and before that, I had a G1.
I have an iPod touch 64gb, didn't want to use a device with insufficient space for my entire collection for my iTunes library, and didn't see the point in having both an iPod touch and an iPhone ... plus, I have an AT&T Blackberry from work, and always think if you have two phones, it's best if they're from different carriers just in case. So for these various reasons, I've been very willing to experiment with Android.
The Nexus One's screen and processor speed make it stand apart from all other phones I've seen. I do like that the Droid has a physical keyboard yet still has a decent/normal physical design. The G1's physical design was a bit goofy. But if you don't need a physical keyboard, I think the Nexus One is at the head of the class right now for Android. The screen is 3.7" 800x480 OLED. The case looks understated and well-designed and feels good in the hand.
Comparing it with iPhones is more subjective because it depends whether the iTunes sync abilities of iPhones are important to you. If not, it becomes a question of better screen and specs on T-Mobile (for now)/Verizon (soon), vs more mature UI and greater built-in storage on AT&T.