I would say usage as a desktop is maybe less than 2%. Servers are much higher 20% - 50% or so. All depends on what you are considering as linux, perhaps a better way to put it would be 'not windows', as solaris is now opening up, and apple is running BSD, and I pretty much consider freeBSD and its variants all part of the same move to linux/unix based operating systems.
The support issue is a big one. TW was able to do it because, if I remember correctly, they made the program on linux (software development is cheaper and easier on a unix based machine, or so I have heard, if you are not using direct x).
Sad thing about support on linux, is that it should not really be a problem (but once the people that use windows switch to linux, they will find a way to mess it up). I have never used joysticks or anything like that in linux, but I have to imagine that as long as you have the right kernel, it pretty much should work no matter what (hahahahahahahhaha yeah right).
I run fedora 3 with 1gb of ram and it looks to me like gnome and kde are happy to swallow as much ram as you give them, but it does not slow my coldfusion, apache, mysql, or sunray servers. In fact with 2 people running sunray thin clients off of my 2.4 ghz fedora box, MS word still boots up faster than it does on my XP 2.8 ghz game machine at home. (I also have a 4x300mhz 64bit ultra sparc system with 2 gb of ram running solaris 10, but that thing is really only meant to be a web server).
erg
