Wow! I work at Microsoft, and did not know how much cool stuff the company is working on as part of Windows Vista! Windows Vista has three broad themes: Clarity, Confidence and Connected.
Clarity: Alt-tab has become so much richer, though I wonder how useful seeing a mini application view when I hover over the application in the taskbar will be. The sidebar is ultimately cool, and SO much richer than a lot of other stuff I have seen this far. Given that I have a widescreen monitor, a sidebar makes a lot of sense to me. Being able to see a real view into the application instead of just a shortcut, the sidebar itself is directly usable. I think I will use this a lot.
Confidence: Parental controls. anti-phishing with community ratings, dynamic protection service. We didn't seem to talk about the anti spyware software the company has built, which I think is really good. I didn't think it would work as well some of the other well known spybots out there, but I actually found it better. With anti spyware, and anti phishing controls in place, my confidence is going up...though having an anti virus software would have been nice too.
Connected: Tabs in IE, finally! This is pretty nice...the feature I liked the most was seeing a view of all the IE windows with a single click, and being able to open/close each window independently. RSS support is also going to become much more native in Windows Vista...well integrated in IE, and a platform that lots of application developers can benefit from.
All in all, pretty cool stuff. I'm definitely excited!