After a MacBook air crash, I ended up on Debian/XFCE. This was more out of necessity than choice, as I could only afford a laptop with very limited resources.

After a MacBook air crash, I ended up on Debian/XFCE. This was more out of necessity than choice, as I could only afford a laptop with very limited resources. I would recommend Fedora (what I'm using at work), if you like stable/reliable packages (Debian also wins here), especially if you're not requiring the latest and greatest everything. In terms of UI, I really like what Elementary OS did, but they don't update their packages with any frequency (the current release is over a year old.) XFCE gives the customisability / get-out-of-my-way feeling that I sometimes want on OS X, but be warned that no Linux UI can match apple hardware and software for gestures. In all, it's a minefield. Format a separate /home, and be ready to jump distros a few times to start with.