System imaging (in the backup area), built in Adware scan, enhanced remote assistant abilities, increased security, better utilization of availalbe ram, native support of IPv6, built in parental controls (my favorite feature personally), windows movie maker, great performance and error reporting features in the performance and monitoring pannel if you know how to use it, windows mail (which allows you to set schedules, tasks, and dates like outlook, to name a few. Not saying it doesn't have its downside, because it does.
You are right, for performance Vista is a bit 'bulky.' Since you'd need 64 bit to take advantage of more than 3.5 gig of ram i'd personally wait for windows 7 to come out. If you can't wait until a possible release date of next year get Vista Home Premium 64 bit.