Which Windows OS do you use. If you are using Vista or earlier, how long do you plan to keep using it?
I have XP installed on a netbook and a laptop, Windows 7 on three, and Windows 8 as dual boot on two of the Windows 7 laptops. I don't use the XP netbook and am going to sell it. My laptop with XP, I plan to keep XP installed on it for now as I rarely use it - it's a 12" model which I bought for portability - but lately I've been using my 14" laptop when I go away.
Still happily using XP and occasionally, one you didn't list; Windows 2000/SP-4. XP does all I need and I keep Firefox inside of Sandboxie. I recently switched from Keyscrambler to Zemana Pro and use MBAM Pro. So far, so good. (We need a 'smiles' crossed-fingers icon).
I like XP, because it serves me well in the way I use my computer. I have no need to upgrade for the moment.
My favorite machine with Vista which I find an excellent OS with the right hardware. I have XP on 3 older machines. Soon I'm going to get a new computer hopefully with Windows 8.
XP on one box, and W7 on the other two. I actually have XP on a 4th box, but it rarely gets turned on and is essentially a door stop (waiting for a door!). I like both operating systems equally... can't really say that one is my favorite... although with a gun to my head, I'd choose W7. Now try to imagine someone placing a gun to somebody's head and telling them to pick an OS. I will say that I use W7 a lot more than I use XP, so maybe that's an indicator of which one I prefer.
I'm currently running Windows 7 64-bit, and have Windows XP plus Windows Server 2012 [based on Windows 8] in VirtualBox.
I'm using Windows XP and I will keep using it until the hardware will no longer be compatible with it anymore.