Bit on the side
We're living in an informational world, and you are an information junkie. The Windows Sidebar is a pleasing piece of tomfoolery that aggregates the myriad stuff you look at on a worryingly regular basis (eg, web news feeds, contacts, calendar, inbox, TV guides) into one place. Best of all, there's an active community making new 'Gadgets' for it, so there’ll soon be handy stuff like Warcraft server status plugins.
At last - something other than a game is taking advantage of that $500 3D card. Vista has a spanky new look: frosted, semi-transparent glass, elegantly shrinking and zooming program windows and softly glowing buttons. The taskbar and Alt+Tab will now show programs - including games and movies - running in glorious real-time, while Flip3D, shown above, is the money shot. It's a scrollable 3D stack of everything currently running.