Its not out as a public beta yet, so I guess most people using it are doing so illegally. We'll find out in a few days when they go to activate it

I'm (un)lucky enough to work for one of the launch partners, so have access to early copies

I like it. It's pretty much just Vista, with the Aero Window Manager improved a bit further. I think its a bit much to say its miles better than Vista :-/ - it's Vista with a tweaked (for the better admittedly) Aero.
The drivers should be good, as it uses the Vista driver model, and most reasonably modern hardware has Vista drivers. Certainly not come across driver issues so far :-/
For an early beta, I was impressed with the speed. OK, I have a decent machine to run it on (Experience index 4.2, with CPU being 7.1).
I generally think its the right evolution. It doesn't deserve a new major version number - thats marketting due to resistance to Vista, mainly drummed up by daft journalists who are inept - its more like XP (Windows 5.1) was to Windows 2000 (Windows 5.0), or Windows 2003 (Windows 5.2) to Windows 2000 (Windows 5.0).
However, I think Vista is the best general desktop OS available, so Win7, being Vista with tweaks, should be better.