it should be fine. you'll have a fresh vista install so no bloatware and then all you will need to install is the pokersites, holdem manager, firefox, then windows defender, and your choice of other antispyware/anti virus. also probaly need instant messaging so i strongly recommend pidgin.
then you can download all your music, movies etc on the mac side.
i would consider virtualization, vmware fusion is supposedly really badass. and you can always upgrade to 4gb yourself for about $250.
http://www.macrumors.com/ great forums. will help you out alot.
tell me how you like your MBP, i really want to get one and i know for a fact my brother is going to get one.
also for a great OS X software google quicksilver. simply amazing.
also did you get glossy or matte screen?
sorry for rambled post