I can't answer that poll cause I'd have to do multiple choices.
We have four machines.
1 - Ubuntu storage space
1 - Mac OSX Tiger - School/Art - Laptop (black macbook)
and 2 - Windows Vista playthings.
Now, the only reason we have Windows on the playthings is because they are playthings. They are for games.
Only reason we have 2 is so we can play with each other.
The Vista machines have given us nothing but grief. In the (almost) 2 years since we bought the first one, it's broken down five times! The other one is barely 6 months old and has been in for repairs once and now has a new problem (turns itself off at random).
The playthings are Acer machines.
We are currently "obtaining" Windows 7 for one of the vista machines in order to repair it's latest vista related death. We have heard good things of it, stability wise, but I haven't got "high" hopes for it's stability.
So it comes down to "what do you want to do with the computer?"
If "games" are on the list, you might need windows, in which case I suggest getting XP or 7 instead of Vista, which is the worst thing since 3.1's "keyboard not detected, press F1 to continue"...
If they aren't, then you're just as well off with Linux or a Mac, functionality wise. (Stability wise you're way better off.)
That's my advice anyways..