I've been doing it for about a year and a half, and have gotten more positive results than any other type of eating I've tried (and I've tried several different things). I have more energy, more stamina, better moods, and more muscle definition. It's by far the best "diet" ever created...probably because it's all natural.
The best part is I can have entire weeks of "cheating" on the diet, and still make progress. For instance, I've been off the Paleo for the past few weeks, and won't resume it till January (except for the few meals I cook at home, which will always be Paleo-friendly). The only drawback with letting the diet go has been lower energy levels, which is perfectly ok during the holidays.