Just as w/ Weston Price's findings, looking at what human beings have eaten throughout our history is really what primal/paleo eating is all about. I really believe that eating a primal/paleo/grain free diet is what humans *evolved* to eat, and that is probably why it seems to work so well for many folks. OTOH, only you can figure out what is best for your own body.
I thought having as much meat as he recommends wasn't good for you?
As far as eating tons of meat, looking at various hunter gatherer cultures, there is a lot of variety in the amount of plants/meat/fat they all ate/are eating (Don at the Primal Wisdom blog discusses some of the variations often). Macronutrients--fat/protein/carbs seem to vary quite a bit. IMO, just do what works/feels best to you. Some folks need more carbs than others, some more fat, some more protein. Some folks (like the Inuit) go totally carnivore and eat little to no carbs, while others, like the Kitavans, eat lots more fruit and tubers and get a large amount of their calories from carbs. Figuring out the path that suits each of us best is up to us, I think.
What Mark recommends is really a produce dominated diet--moreso than meat (I've realized this more recently re-reading the Primal Blueprint book). BUT, you will still be getting the majority of your calories from fat/protein (meat), even if you eat a lot of produce, as meat/fat are far more calorically dense than veggies/fruit. Whatever the case, it does not have to be a meat heavy diet. Mark's wife actually follows the PB but does not eat meat--just fish and eggs and dairy I believe. And there is at least one vegetarian currently involved in the primal/paleo/grain free thread. There are endless possibilities when it comes to going grain free/primal/paleo/etc... It is not one-size-fits-all.
Is it really healthy?
IMO it is a very healthy way to eat (as I've never felt this amazing before). I also think the only way to know if it is healthy *for you* is to try it (while being sure to continue reading up on it to see if any changes you experience are in line w/ others...There is the 'low carb flu' which I personally think is related to gluten withdrawl for many folks--stuff like that in the beginning might make you feel like it isn't right for you, so being informed on what can happen as you make the change is helpful. The MDA forums are awesome for that, and our primal/paleo/grain free thread here rocks as well.) I've never felt better personally, and look at this way of eating as a lifestyle choice--not a diet.
Has anyone lost fat by eating primal?
Weight drops off of me when I focus on eating mostly meat, veggies, fruit and fat (like coconut everything, ghee, etc.). I've absolutely lost fat eating this way. I also lost fat when I first dropped gluten, dairy, corn and soy. But eating primal/paleo-esque has gotten me thinner (in a good way) than I'd ever been before. I'm also a lot more energetic and just feel great. I work out quite a bit now as well--which has been very much inspired by the info at Mark's Daily Apple along w/ my newfound energy--which has definitely impacted my overall body composition. I didn't go grain free to lose weight though--I was pretty satisfied w/ where I was pre-primal, but it totally smoothed me out and made me feel much better overall.
I'd say it absolutely works for me, in more ways than I had realized it could!
HTH!
ETA: I, like the previous poster mentioned, also do a TF primal/paleo way of eating--so I continue eating lots of ferments, bone broth, some liver (where I can get it in) etc. Still focussing on nutrient dense foods, but w/out the bother of needing to sprout/soak grains or legumes (unless I'm making them for dh or ds, which isn't all that often now). So it's kind of like simplified TF in many ways...