I loaded it up on a stock Gateway P4 system here at work, but I didn't dual boot it, as I didn't want to deal with potential issues on that end. Here are some of my thoughts:
Least interactive install of any version of windows I've used (pretty muche everything from 3.1 up), which IMO is a good thing, fewer reeboots, less clicking and such. While a corporate IT dept. will usually be doing unattended installs, it's still nice to see how the process is going to work for the average end user.
The network detection / setup is a little more coherent than it has been in past versions.
Only two devices were not detected and configured properly after the initial install - An epson scanner (which I did not even realize was still connected, so I had no expectations of it being set up), and the Creative soundcard, which a quick visit to Windows update fixed.
The interface is very pretty, and if you use OSX and/or Linux you will see lots of things that remind you of those GUIs. I think that the interface as a whole is improved over XP, but that's ultimately a matter of opinion. It's nothing too different from XP, just more refined.
I'm not running a state of the art video card, and only 512MB of ram, but overall I'd say it is running comprably to XP, though I have to start loading up some apps and really compare.
I'm very interested in finding out more about the Bitlocker disk encryption, which I haven't played with yet. The idea of having my personal machines disks encrypted is sweet, but the idea of the machines here at work encrypted by an end user is a potential nightmare waiting to happen, I suspect
It is certainly not ready for prime time, but if you are the type that likes to play with the new toys as soon as you can, I'd say it's worth the download. I have heard from numerous folks saying stick to the 32bit version regardless of processor, as driver support is not particularly good for the 64bit yet.