This guy I find very interesting - he regularly writes for scientific mags (no, I dont read them) and has a very scientific approach in his newsletter (which info is unfortunately is not available online). Here's a good link for a summary though -
http://www.thepaleodiet.com/faqs/The message:
we had a pretty standard diet for a huge timespan, this has only changed since the introduction of farming (of grain in particular).
Our bodies have not adjusted towards this relatively new food etc. etc. (Of course sugar is another new food for us...)
So his approach is to chuck the carbos (concentrated/processed - grain causes us most problems, but also potato, not sure about rice). Also not eat grain-or-corn-fed beef (as it's an unnatural diet for cattle too which causes a lot of health problems for them and indirectly for us as well)- rather eat grass-fed beef (I dont know about pigmeat - pigs would have eaten anything).
And no again, I havent tried it

but I do eat more protein now than I used to.