I've also got an MSDN subscription and have been running Vista on my two-year-old tablet since Thanksgiving.
Overall, I like it.  Some of the changes to Windows Explorer/My Computer actually are easier to use (at least for me).  The handwriting recognition does seem a bit improved, too.  Really, most of the little things add up to a pretty nice whole.
The Sidebar, which I thought I was going to hate, has actually had some uses -- mainly in checking weather, but there are some other toys.  It comes turned off, by default, too.  There is definitely no gun to the head.
The permissions nanny is nowhere near as annoying as I thought it was going to be.  In fact, I barely notice it even though I do programming, which is one of the touchier things.  Something to keep in mind, though, is that new directories are set to "read only" for everyone, by default.  I had to change the directory settings for PCGen to get it to work.  But, that was a pretty quick, minor change.
The down sides, so far:
Drivers -- Yup, some of them are tough to get.  My special tablet PC buttons (like the one to quickly rotate the screen) don't work.  I should check for an update now that the public release is upon us, though.  Otherwise, my drivers have all worked fine, except....
Pocket PC -- The old ActiveSync software isn't compatible.  Vista won't even let you install it.  There is a new tool that I absolutely cannot get to work right, though.  Technically, it's still in Beta, so I'm not that concerned by a glitch.  Still, having that sort of product in Beta at this point seems like pretty poor planning on the part of MS.
Power consumption.  My battery life is a bit shorter (maybe 15-20% less) under Vista.  But, I also have it set to max performance.  Speaking of which, my mid-aged, low-horsepower, computer is moving at a fine speed with Vista.
I've been looking at desktops lately.  I've actually been holding off until Vista is available, though.  Since my kids will be making quite a bit of use of the new machine, I definitely want the extra security on their accounts.
Oh, and I've been using Office 2007, too.  Very nice.  There are a few tweaks to existing tools (color picker, autoformatting) that are really nice.  The new ribbon control took some getting used to, but I think I actually prefer it, now.  At the very least, I find myself wishing for a couple of the improvements at work (where we run 2003) quite often.