@ Urza - I guess my response falls under your first category. To be clear, however, XP is now what, 7 years old? It is super stable, at least in comparison to what it once was. Just about any device or software you'd want to run on it runs well, my system has 2 gigs of DDR2 RAM, and I can do just about anything on there, multitasking wise, and rarely bump into any issues. The following is a more in-depth response, explaining why I have desktops running both XP and Vista, and prefer the former quite a deal more. No flames or malice intended in this post, sometimes I use the Vista PC without a hitch. This is not that story though.
Now one of the other computers in this house is similarly spec'd to the XP PC, it was picked up only a few months ago, and sadly was pre-loaded with Vista Home Premium. I have a lot of the same programs on both PCs and one is a clear champion in getting stuff done, while the other one forgets how to wake up from sleep mode.
I liked the idea of Vista initially, I actually beta tested it what, two years ago, or whenever the public beta started... but I think the big problem Microsoft is having is that they tried to do too much with Vista and failed on a lot of fronts. The new FileSystem... what happened to it? I don't know. There are thousands, hundreds of thousand, maybe even a million programs for Windows, and they worry about backward compatibility, why couldn't they have just said... "nope, this is a new OS, you're going to need new shit to get this working on your device" Not including the whole debacle over having half a dozen different versions of the same OS shipping. XP had what, 3? Home edition, Professional and then 64 bit, right?
And its not just the fact that my printer which says "Vista compatible" on the manufacturer's website works fine with the one desktop running XP but the Vista machine "forgets" it has a printer and then re-installs 6 Epson printers and forgets which one is the default.
And yes, there are days I get on the Vista machine (oh, it was pre-loaded, with no way to downgrade easily when purchased) and nothing ill happens, it just does it job. Sometimes it does.
XP isn't the end all be all for OSes. It is dependable though, especially in recent years. I cannot say the same for Vista. The fact that people are irritated by the lack of compatibility, everyone dragging their feet on drivers, eating RAM for breakfast, the UAC, and other assorted goodies, if someone wants to avoid issues, isn't a complete noob with a computer, why in god's name would you recommend something that isn't going to have the kinks worked out for at least another year, even after SP1?