I went from the myTouch 3G to the Nexus One.
IMO android needs some more heavy polishing to be in the same league as the iPhone. That said I do like the N1 (minus Google's bungled support system). I don't feel it qualifies to be called a "Superphone". To me it's like having a smoother scrolling myTouch with a bigger screen and prettier interface.
Is it worth the $530 bill? At present I would say no.
Will it be worth it after a few updates? I'm hopeful it will be!
One thing worth noting....Had I have not had missed call issues with the myTouch 3G (had two of them, both had the problem). I wouldn't have gotten a Nexus One. Knowing what I know now after owing the N1, i'd have been happy with a myTouch with working calls.