While the reviews are mixed from teachers as I finish up the rollout of new Vista-running PCs, the reviews from students are almost universally positive. Maybe it's their fascination with shiny objects (most people will agree that Vista is, at least, pretty), but I think it says a lot more about kids' general flexibility in all things technical.
The bottom line? They just get this stuff. Does it have a web browser? Check. Can the web browser handle Flash and other fun content? Check. Can they type their term papers? Check. Can it play music, either streaming or downloaded? Check. Video? Check. Then it must be good. A typical teenager's view won't be colored by Jerry Seinfeld or early driver problems. Short memories and short attention spans mean they want to know if it works right now. And guess what? In most cases, Vista does just that. It works right now.
Of course, the same can largely be said of Mac and Linux if we ignore hardcore gamers. Most kids have largely recognized what only a small number of adults have come to grips with: the OS is irrelevant. It's all about the web browser, folks. Google Docs, Zoho, and OpenOffice all work quite well on any platform (the former even works fairly well on mobile platforms).
So the kids like Vista. They get their work done. Does that mean we should use Vista? It's probably a better choice than XP at this point. What it really means that the kids are fully prepared for whatever changes you throw at them. While your teachers might be a different story, point the kids to the apps they need and they'll probably be good to go.