Okay. This thread wasn't supposed to degenerate into bashing this or that OS version, but in the interests of balance I have to say I have upgraded my PC, my Dad's PC, and my Mum's PC from XP Professional to Vista Ultimate and, in general, it has been a positive experience. Admittedly my Dad's installation had some teething problems we eventually identified as due to an old sound card driver ... once fixed it's been fine. I know YMMV but for us the bottom line is: we like Vista. For us Vista has not been pants.
Unfortunately, OS Religions seem to be like certain Traveller Version Religions - there are some really faithful adherents of the One True Faith (c). Bottom line: if it works for you, and does what you need it to, that's all that counts. An OS is simply a method for you to interact with a computer to make life easier. The hardware (at the personal computer level) is pretty much identical for all OS: Linux (or GNU/Linux if you want to get fussy!), OSX, Windows. Heck - the OS are pretty much identical as well (and there is no need to get into who stole what from who - ALL OS steal ideas from each other, which is why (to me at any rate) they all pretty much are the same, visually as well as operationally).
There are advantages & disadvantages to all of them. To paraphrase from another board about "which Spinward Marches is canon" (re: T5 updating the Marches, the Mongoose version, BTC, etc): each OS is best for the person that chooses it for the reasons that they choose it.
I use Windows XP - it has the tools I need to work & play. I use Linux at work, telnetting in from my XP machines. But I could use ANY OS for that part of things - heck, I can even telnet in using my phone, and it has a real keyboard as well (not that I actually use that. Go figure!)
But as per the Traveller canon/version stuff - people will argue continuously and vigorously that their OS is the one true version and all others are horribly wrong. I'm OS agnostic: as long as I can do what I want/need to, I'm happy (and I've used Apple OS, Linux, Datapoint's RMS, various UNIX & Linux systems on a wide variety of platforms, IBM's odd VMS stuff, and MS-DOS through XP. They are all the same essentially: a way to edit files, access other computers, and run programs. Who cares what OS it is?)
I think the purpose of this survey was simply to see who was using what so that a developer could focus on the largest commercial OS to maximize both productivity & his potential user base. Arguing the merits of one over another is, to a point at least, interesting, but ultimately as useless as arguing which version of Traveller is best: it is a personal preference.