Vista RTM was horrible, even on a powerful machine. MS really screwed up by rushing it out the door when it wasn't ready for prime time.
Rushed? You call SIX years from the release of XP in 2001 to the release of Vista in 2007 rushed?
And don't try denying it: the one reason why Vista was in fact late was because XP and XP SP1 was being torn apart by an over abundance of security flaws and other instabilities, and Microsoft had to take many important developers off the Longhorn project in order to focus primarily on XP SP2. It's amazing how short peoples memories really are..
But back on topic, if you'll forgive the unavoidable rant.
What to do with my Vista x64 Ultimate licence? I was originally planning on building a Media Center PC for my dad, link it with my Windows 7 machine and stream the media. Get him off the old-fashioned style analog TVs that can only do one thing. But I've found a network-capable Media Player with PVR support that will cost be about half us much.
So I guess I'll probably end up saving the disc along with the rest of them, XP, 2000, ME, 95 and 3.1 - untill I need them.
But make no mistake, I went dual-boot between XP and Vista, and abandoned XP about 4 weeks later in favour of Vista. I did the same two years later with Winodws 7. I dual booted, but THREE days later I took Vista off in favour of Windows 7.
I've been using Windows 7 since the first public BETA Build 7000, I'm now on the RC Build 7100, and I'll most defintely be using Windows 7 Ultimate when it hits store shelves (maybe a month or two earlier - I work at a computer store

).
Vista is the OS that Microsoft "finally got right". Windows 7 is Vista done even better.