For that price I'd definitely go with the Nexus S. Really good phone but no FM radio or SD card slot
The develpoer community is spot on for the Nexus S and I think that is the way I will jump. It is for my son later this year and he is currently using one of my old phones, a ZTE Blade, but it pains me every time I see that phone. In many ways I really think I am getting the phone for me to play with before I hand it over to him. Every Android device in our house is rooted and only my daughters cheapy 7" tablet is still stock. So I am looking forward to getting the phone and trying various custom ROMs out. Then of course I will default to Cyanogen Mod as always seems to happen.