I've lost 16kg (162 pounds to 126 pounds) in 12 months from hugely cutting down on sugar and carbohydrates, so I totally agree with how those two food groups in particular contribute to significant and sustained weight gain.
However, the problem with the "paleo" way of thinking is that it's massively underpinned by the natruallistic fallacy (i.e, if it's natural then it MUST be good). It's great to see these people have introduced more variety and balance into their diets, but it almost seems like they've just gone from one end of the spectrum all the way to the other end. There is a case for balance!! Of course you don't eat a diet 70% made of carbohydrates, but it also doesn't mean you can't have the odd bit of bread, cake or sugar every now and again alongside your healthy way of living.
I also found the bit on exercise far too extreme - I understand that they're trying to appeal to how our ancestors lived, but that by no means demeans other forms of perfectly reasonable exercise like running or swimming, etc. I don't understand why climbing a tree is going to be significantly better for your health than doing weights or a run at the gym.
Great documentary if you want more of an insight into this way of thinking - it's just far too "absolute" for me....