I use Gentoo, but Gentoo is one of the more newbie unfriendly distros. It's pretty powerful if you decide to be a hardcore Linux user, but considering the install takes like a whole day (you compile all the software from source code) with a lot of commands, most people would probably find that annoying. Gentoo is really flexible, letting you construct a Linux setup to your tastes, but that also makes it a tad daunting.