Some new things in this version:
May see system improvements using 512MB Ram or more. Will use less memory at start up.
The Windows Vista Aero Assessment process that runs after installation will display information regarding new and key features included with Windows Vista. (This is similar to the way that the Windows XP setup process displays information regarding the product.)
The new Windows Vista Basic theme. (this is more for ppl who cant get full Aero cuz of their video card/chip)
NVIDIA Display Driver issues should be fixed, so testers are urged to look out for any issues that persist with their NVIDIA cards.
More icons added to start menu
More tweaks to User Account Control.
UPDATE: (will try to post more wheneva I find more info)
Flip3D has a slightly different angle (like it really matters??…lol)
MCE (Media Center Extender) is improved, works good and it has a light aurora living in background
MCE has new sounds and animations
Aero cursors are activated by default
New icons are present in this build