for the time being, i will be an OS priest lol,
choosing an OS depends on the area you live in, the country your from, and what you use a computer for...
the simple users wouldnt even know what an OS is, so the might think a normal computer is a computer with windows theme and microsoft office 2003 LOL.
Linux, is mostly known for geeks, programming and all sorts, since it's an open source program, but simple users ( like me ) dont use it, since the installation files for linux are completely different to Windows ( for example, when i installed Linux Ubuntu 7.04 feisty fawn, i tried to install some programs by an .exe file but it didn't recognize it) and i was quite disappointed, so without even trying to fix, although i know there is a way round it, so i overwrit Ubuntu with Windows XP Proffesional SP2. (thats on my other pc)
I am currently using Vista Home Premium on my main desktop pc, and the only reason i want vista is because everyone is using it, and when one day XP falls, i will have to get vista again and get used to troubleshooting it, but luckily all my vista problems have now been solved using no "internet Vista-tools", all you have to do for vist, is tweak with in the system.
Conclousion...Windows Vista.