i already have an am2 board, and depending on how the new chips perform i might snag a cheapie (my 2.85ghz brisbane 3600 is good enough for now lol).
basically man, am2+ chips will be compatible in am2 motherboard, and i also believe that am3 chips will be compatible in am2+ boards and am2 boards as well. if i'm wrong i'm sure someone will correct me, but that's my understanding, if i remember what i read correctly lol. using an am2+ chip in an am2 board will lose you like 5% mainly because of the way the am2+ boards will distribute power, but using an am2 chip in an am2+ board won't get you any benefits over an am2 board since the processors don't support the new features. the faster ht link will be pretty much useless for most desktop applications, as even the current 2ghz bandwidth isn't even nearly being touched.