I upgraded to Vista, and downgraded as soon as I discovered the the DirectSound HAL was history and had taken EAX with it.
Only two of my friends upgraded to Vista, they both downgraded. One did go to XP x64, however.
I run a small-business network of around 20 PCs. You will *never* see Vista on it. I know Microsoft don't care about a small-business network, but still, its more likely that you'll see Kubuntu in the near future.
I remember XP's release. At the time, I was running 2000 and all my friends were running 98SE. They all jumped on XP because it was a move from the '95 branch of Windows to the NT branch - it offered a dramatic improvement. I swore by 2000 and promised never to upgrade. In the end, I did upgrade because XP booted faster, ran faster, didn't require petabytes of service packs (at the time) and provided a few new features.
Compared to 98, XP offered a whole new operating system. It was built on the NT fork of Windows, it featured *real* user accounts, it supported NTFS.
Compared to 2000, XP was a marked improvement. It booted incredibly fast, it ran fast. It featured some genuinely useful improvements in the U.I. It even offered a nice visual refresh (which we all disabled).
Compared to XP, Vista offers nothing more than Aero. It boots incredibly slowly, it runs slowly, it requires awesome hardware. It is a "regression" in many senses of the word - i.e. features have been removed. One of them is EAX, my pet gripe. Instead, it offers security-by-multiple-annoying-padlocks: UAC and defender. (Not real security but you hope there's enough layers to annoy any crooks into leaving.) It offers an *interesting* visual refresh: Aero.
Microsoft *should* have taken XP and removed the cruft: everything that's not the operating system. (Firewall, IE, MSN apps, messenger, etc.) They should have optimized some code to give it a performance boost and added Aero, which is a nice idea. Their new, controversial memory manager could, arguably, have found its way into the OS. DirectX 10 should have been added, but the regressions from DirectX 9 should not. Basically, they should have made a good, bare-bones OS: Windows + notepad + calculator + nothing else.
Once they had polished up their bare-bones OS, they should have taken the features that were removed from the OS and turned them into bolt-on applications: Microsoft Firewall, Microsoft Antivirus, MSN Suite, Microsoft Internet Explorer etc. These should be bought separately. Each of these should be fully-functional applications that can only be used as a bolt on to the bare-bones OS.
Consider a corporate: they would buy lots of OS licenses. A corporate would probably be running hardware firewalls, so they wouldn't buy the firewall. They would buy the antivirus, if it was good. A home user might buy the firewall in addition to the other two. I would only buy the bare OS. This product structure would be perfect for everyone. It would even satisfy the competition courts.