Ubuntu for me. But i use mac osx and windows xp at the uni sometimes. I will never go back to windows now on my main pc because it's a flawed product. All those viruses...
It's definitely a flawed product, but so is just about every other OS. I don't like the way it presents the user with a desktop long before it's actually usable, or the way it allocates huge amounts of storage to things like the recycle bin or internet cache by default, or about a thousand other boneheaded design choices MS has made, but I'm convinced viruses are mostly a matter of user error.
I've been using windows for over a decade with constant internet connections and no AV software, and not once have I had a problem with a virus. It's not like I have my system locked down, or avoid sketchy websites, either. I've had to re-install plenty of systems which did have viruses and malware, and in almost every case, the source of the virus was either the user falling for some lame trick prompt on a website, or careless downloading from P2P networks.
An experienced user should never have an issue.
