Not as bad as people say.
Started with Vista on a new Laptop. Took a bit of working through the cr@p I don't need and turning it all off but so far it looks like HP did a good job on the packaged OS build and I think that this is the reason why I had a good experience. Most of the bloatware was from M$, HP only included a couple of programs in the build.
Only real issue I have is that Outlook 2003 on Vista cannot connect to a Microsoft Exchange Server as it did when running on Win2k - so after having migrated all my office settings (worked fine) I have to sort out that issue, there are still a few possible solutions so although annoying it is not a show stopper.
Cleaning up in general took a bit of effort (don't want M$ applications in my face at the top of the list of the Start Menu and Side Bar junk or UAC) but to be honest getting the OS to look like I wanted it (and configure the services I wanted or did not want) took no longer than resetting the application configurations to my norms after I had installed all my apps and tools I use. I know Mac does this config migration for you automatically when you install on a new machine and connect your old one but I have a wide range of apps and with that choice and diversity comes the effort of setting all the preferred options, there is no free lunch in this world. For some apps I just copied config files over.
I'm now on a machine that is now tidier and more refined than XP (that I use on another machine) or Win2K and doing what I did before. Having said that, I would eat my dog before I performed an OS upgrade to Vista, I think it's a fresh install type of change that is the right time to choose to leave XP (such as I did when a change of hardware occurred). I'd love to see this happen on Windows as smoothly as a Mac "can" do it (if all goes well) but as I have stated elsewhere the relatively poor range choice of Mac software makes the effort I just described above wothwhile, for the moment, in order to preserve my massive range of application choice. Anyway, I've got VMWare Workstation installed.
Hardware I used was an HP dv9670ed: 4Gb RAM (Vista only uses 3.1 of this) and 2GHz Dual Core Intel Processor.
My summary, "Acceptable, M$ could do better".