Who dosn't use windows? it's features, and everything far outweight the others, although it does tend to be more Vulnerable to viruses than others it seems, but it's worth it imo.
Plenty of people use Mac. And after my old laptop's hard drive crashed, I had to run an OS off a disk so I used Linux. It actually wasn't bad. It's great if you want something simple.
Linux is a powerful operating system for those who get to know it well. For this, along with security, I primarily use Linux Mint on my system. I do have Windows XP and Windows 7 installed as well, so I have maximum compatibility for games and some other software.
Honestly, as a Linux user, I can say it is very impractical to NOT have a multi-boot with Windows. People can run Windows programs in Linux using Wine, but it's not perfect - most programs have issues, and many are unusable. Hardcore Linux people will piss and moan about stuff not working in Wine, but they treat Microsoft like the Nazis and refuse to touch anything with its name on it. Seriously, these people should just swallow their pride and keep a Windows partition handy.
But aside from incompatibility with Windows software, I like Linux a whole lot better. :D
although it does tend to be more Vulnerable to viruses than others it seems
A rather misguided view in my opinion. Its the most popular and therefore the most targeted. If one of the other operating systems were in Windows place, then that other operating system would suffer the same problem.
As for the actual topic, I use windows. I've never liked the interface for Mac OS and never really tried any others. I've occasionally had to use a Linux operating system at work, its alright. At home its windows, purely because I like to play my games without having to mess around with stuff (I could do the messing around, I am just lazy).