I've recently learned couple of little tidbits about upgrading to Windows Vista, and thought I'd share with the world.
There are two ways to install Vista, an upgrade or a clean install. The upgrade option will preserve your existing applications, files, and settings; it's intended to be a seamless upgrade with everything working pretty much the way you had it. A clean install will back up your previous installation (so you don't have to make your own backup first), but will not transfer any settings to the new OS. A clean install takes maybe half an hour; an upgrade can take all day.
With previous versions of Windows, you generally had to boot from the CD, then begin the installation. With Vista, you can run the installer from the DVD while your existing installation of Windows is running. This means that if for some reason your DVD drive isn't bootable (for example, I have an external FireWire DVD burner that my BIOS doesn't know how to boot from), you can still install Vista (but be prepared to connect a bootable DVD drive if anything breaks in the future).
However, be aware that if you bought the upgrade version of Vista (as opposed to the more expensive full retail version), you cannot install while booted from the DVD; you must run the installer from a working system. The full version of Vista will let you do a clean install (but not an upgrade) while booted from the DVD.
You can do a clean install from within Safe Mode, but it will only let you do an upgrade install from Normal Mode. If something is preventing you from booting to Normal Mode, you'll need to fix that first, or just do the clean install.
Booting from the Vista DVD is a much friendlier experience than in previous versions of Windows where the setup program looks like it hasn't changed much in the last two decades. In fact, it looks very similar to most modern Linux installers - you get a full GUI, an easy-to-use disk partitioning utility, recovery tools to fix a broken system or diagnose hardware problems, and convenient access to a command prompt that doesn't require your Administrator password like XP's Recovery Console did. I haven't tried it yet, but running GUI apps from your hard drive via the command prompt on the DVD might work.
I definitely think Vista is an improvement over XP. They've cleaned up a lot of stupidity that's been in there for more than a decade. Some people are freaking out about DRM, but as long as you don't run Microsoft's media applications, I don't see that being an issue at all. Sure, plenty of stuff is newly broken - Microsoft has said they're already planning to release Service Pack 1 around October, and there's a ton of third-party applications and drivers that are buggy or unavailable - but people complained about exactly the same thing when Windows 2000 first came out, and many of those same people now say 2000 is their absolute favorite OS. Give it time.
However, would I recommend a Vista upgrade to the average user? Nope. Upgrading to Vista on an existing PC is usually a bad idea. If you're happy with XP, save your money. If you're not happy with XP, why not try a Mac?