Well my experience is positive overall. Very nimble around the os bits & bobs itself - the old chestnut is true that whilst you don't care very much if a mail merge takes 40 rather than 30 seconds, but it gets right up your nose if you have to wait five seconds to open a folder has been very well adressed in 7.
UAC has been throttled to everyones relief, many error messages in media centre, audio is troublesome, but then again I've hitched my wagon to Creative so that's my own fault really. It doesn't come with windows mail, as a result of the anti trust rulings I understand, so you will have to drop gmail, thunderbird, whatever in to do that. Devices hooked up to the machine are handled beautifully - plug a phone in for example & a photrealistic image pops up with al the options you may want for managing that device. You now have libraries for documents & media which are a cinch to use. Quick launch is gone. Instead you get similar icons that launch preview windows just above the taskbar. So if you have four firefox sessions running, you get four little preview windows if you hover over the firefox icon. Takes a little getting used to, but works well I think.
Network setup is automated as in Vista, but is smoothed out a little - you can still dive in to the gubbins as necessary, the control panel is much improved & that's about as I've done with it.
Essentially, it comes over as a polished iteration of Vista, the two main conclusions for me are it looks much better & runs far more sweetly.