I used it temporarily and it managed to mess with Vista so bad that everything reset to Internet Exploder on it's own, and refused to find Firefox at all until I removed 3 and reinstalled 2. It also, iirc, broke a bunch of pages that validated as strict CSS 2.1 and XHTML, which didn't make much sense, since that should've been one of the first things implemented (or in other words, taken directly from 2).
I'll definitely be looking out for the stable release, though I desperately hope they clean up the new drop-down on the URL input... twas ugly and made it extremely hard to find pages I wanted without just typing them completely in.
As for Vista... It's just like any other new Windows release. Looks nice, works acceptably, and if you don't have three times as much memory as last year, leaks it out like a sieve and needs to be rebooted constantly.
My CPU usage hardly ever spikes over 30% - it's idling right now at 13% with PHPDesigner,WMP,Firefox,Task manager,IM apps,Word and a few other things. I have a plain old 3GHZ processor...it's about 2,3 years old.
"What everyone seems to forget is that while knowledge certainly is something - it's the implementation of knowledge that brings power" - Andres Galindo.