I just ordered a Galaxy Nexus as well. My contract on my iPhone 4 is up in a few weeks and I've been set on either switching it over to StraightTalk or to Tmobile. I decided I'd give Android a try first ... while the Galaxy 3 is tempting with the removable memory and better specs, I didn't want to lock into another 2-year contract. The GN seems like a great deal for a contract-free phone right now, and I figured if I waited until the next one released, then of course it would be either on contract or an extra $300.
I figure that I'll get a few months of using the GN to determine whether or not I want to keep it or sell it and go back to iPhone and AT&T.