I've used it, but I don't think I will switch until it is broken-in a little more. By broken-in, I mean that any new OS has to go out into the real world for a while so developers and consumers have some time to work with it to find all the problems and incompatibilities. This could take years. It does have potential, but the full extent of its potential will not be tapped until software is written with Vista specifically in mind.
It is indeed a resource hog, but relatively so when compared to the release of XP in 2001. Consider that a top machine back then had a P4 2ghz chip with pc 133 ram. Many computers still had PIII's in them. Running XP back then was even more dramatic in the resources department. We run XP now on dual and quad core machines with dual gigs of ram (more available for 64 bit of course), raid drives and soon to be commonplace solid state drives, etc. When we load up Vista, yes it is slower with Aero-glass, or whatever they are marketing the gui as, but it is still relatively faster than XP when XP was first released.
The major issue with Vista, and to a lesser extent, XP, is that Microsoft is making OS's "easier" for the consumer, not the IT guy or even the moderately proficient computer person. They are making these usable for grandparents, soccer moms, and a whole slew of people who are in all reality computer illiterate. I often associate Windows OS to the McDonalds registers with the pictures of food on them. People can't be asked to read anything anymore, they need glittery gui and iconography to navigate through even the simplest tasks with computers. My first computer did nothing without programming 5 pages of basic into it first.
My suggestion is to stick to XP for the next year. That is when Vista will be ready for prime time. If you are really interested in shiny gui, use XP with windowblinds. You'll even get the bloated vista feeling as a byproduct, but all of your current software will work.