I've been using Fedora Core 4 for the past month or so - my first foray into the world of Linux, although I had used Unix at Uni some 10 years ago. It was very easy to set up (probably helped by being on a physically separate hard disk to my Windows install), although as Craig says it does use GCC4, so you'll have to install legacy drivers - there's a sticky HOWTO thread for details if you decide to go with this.