Windows 7 RC, Visual Studio 2010 Beta, Office 2010 beta, anyone in?
Right now at home I'm using windows 7 and I have to say it so far is smooth and fast. Probably my favorite iteration of the windows brand. It's some of the little things which you take advantage of that are so much easier to do. The side-by-side functionality and vertical maximize are especially usefull. The gadgets not being restricted to a sidebar is nice as well. One of my favs has to be the Desktop Slideshow and fitting options it has. Also the way the new taskbar is managed is great, it takes a little getting used to but it's much more efficient than the old one. Saves a TON of space and doesn't group it in an annoying way.
I just got the beta for VS 2010 and haven't used it much but from the videos I've seen it has some cool stuff. Don't know how big the managed extensibility framework is to extend the editor itself, but it looks cool.