I'm reading the Primal Blueprint, and I must say that I really like this Mark Sisson guy. Granted there is a lot of overlap between Paleo and Primal, but I think the Primal mindset is a bit easier for me to Grok.
One key difference is Saturated Fats. Primal is perfectly fine with these from most sources, the biggest consideration with fats is striving towards that lovely 1:1 or 2:1 Omega6:Omega3 ratio.
Primal seems more okay, on the whole with butter and things like that as well. It subtle. I think Robb Wolf makes some great points in The Paleo Solution, but I can't help but love Mark's book.
Best thing I learned and have practiced from The Paleo Solution: The 30 day rule. Just try it for 30 days, and then see how you feel. I'm pretty sure artificial sweetners have been giving me a fit. I've mostly cut them out from my diet.
I'm drinking a diet soda right now, actually, and if I'm right I'll really be feeling it later. Abstaining completely from non-paleo food sources for a while really helps you learn the "good normal" way for your gut to feel rather than the normal you may be used too.
The best thing I've learned so far from The Primal Blueprint: Don't worry about calories, meal frequency or anything like that. Eat the right kinds of foods at least 80% of the time and let yourself get into a rythm that works. If you don't feel like breakfast, skip it. It's actually good for you.