There are a lot of new stuff in memory management for Vista, for example: it can detect faulty memory address, and dont use it, so bad memory wont cause BSOD, the whole memory manager have been updated to reflect todays memory sizes, superfetch for faster
program start and USB memory for cache....etc.
Transactional File System
always everybody forgets one of the biggest: DWM (not part of Aero, and not backported to XP)
every win app refreshed (maybe Paint not, but who knows)
new look and feel (Aero, not backported, with new backgrounds, new screensavers, new start menu, new windows switching etc)