A note about VS versions, there basically no point in using 2008 or 2010 since 2012 is compatible with XP. 2008 technically will give you compatibility with WIndows 2000 as well, but I don't hear too many people complaining about that. All versions past 2005 drop 9x targeting support.
That's not quite true. You need Windows 8 to run the 2012 compiler, as stupid as it is. I'd like to switch over to 2010 but I'm having problems getting the project to convert so unless I manage, it'll remain on 2008. Sadly, the 2008 version is rather buggy but it's still better than the constant fight I have with 2005. For some reason it just doesn't want to play nice with my system so I just gave up and switched compilers.
Perhaps I am not getting the picture, but why not use Visual Studio 2012 (or even 2013, soon to be released)? Is it just because of compatibility with ancient Operating Systems?
No, it's because I do not have Windows 8 (outside of a VM for Windows Phone development) and I'm not particularly interested in screwing up a well working computer by installing a broken OS.
That argument only applies if we're talking primary computers. Some people, such as myself, have retro gaming rigs you know.
While it's irrelevant for GZDoom since I don't believe Graf supports GeForce 3/4/FX hardware, a high end Pentium 3 + GeForce 4 seems to be a fairly common build to play old DirectX games on Windows 98. (Geforce 6+ removed support for some feature and all ATI cards have issues with some DOS games like Commander Keen.) These machines are capable of running ZDoom or Zandronum, but they're not Internet browsing machines. Still good enough for an extra player in LAN games.
I don't think there is anything preventing GZDoom from running on such old hardware - but it's clearly not an intended target. If it wasn't for the shitload of Intel GMA based systems I'd have already scrapped all pre 3.x GL support by now because it's a major pain in the ass to keep all that compatibility crap in.
So while I won't intentionally break it, don't expect me to invest any time in that old code.
(At least I'm not like the Doomsday devs who probably killed off half of their user base when ditching XP for some questionable 'convenience'.