You're a couple of days late or else you could have gotten the Nexus for free.
I haven't upgraded from my Nexus one to a nexus s because it's not really much of an upgrade, and I'd rather have an HTC phone over a Samsung. The Nexus S feels very plasticy and cheap. Having NFC would be nice but it's not a deal maker/breaker. Having a Nexus phone is nice though bc it is vanilla and you will always get the latest updates first. I'll stick with my N1 until the next nexus phone comes out.
I don't like the size of the Evo, but I'd get an evo, root it, put vanilla on it.