So far I have to say that I'm pleasantly surprised at the speed and stability of Windows 7. It is much faster at most things. One thing that really used to annoy me with both WinXp and Windows Vista was how long it took to display a context menu when I right clicked on a file. It is much, much faster on Windows 7. I've had no serious crashes and no app compatibility issues with apps I've installed on it thus far.
Today I'm diving into development so installing Visual Studio 2008 and it went off without a hitch. I have to say things are looking good for Windows 7 so far.