I played this for a few hours with a friend, my thoughts so far:
Food rots absurdly fast, but it's also very very easy to get. I guess it's balanced, but it also feels really pointless - I never once starved or really had to even worry about food at all. It's a complete non-issue, I had more berries then I could ever eat just from trying to collect fiber.
The EXP system is an interesting idea, but in practice it's just a stupid grind. After a while, my friend and I were just clearcutting every single rock, tree, and bush and murdering every dinosaur we could, and leaving all the materials/meat to rot because we only needed the exp. At least in a traditional MMO the npcs can theoretically kill you and there's a token plot to keep you entertained while you grind, but trees dont fight back and rocks don't have any storytelling.
Engram system too seems interesting, but fails. I understand what they were going for - if you can't make everything yourself you are forced to group up, and maybe if people are forced to group up they won't just randomly murderbone everyone they see. But it was a big PITA to coordinate even with just two people, every single level we'd have to coordinate what skills we were going to buy, and it was worse because there's no indication what some things do, and you have no idea what something is going to unlock later unless you google it. I also can't imagine how annoying it would be to play with 3+ people and be unable to get, say, an axe because the guy who made axes was not online. I feel like even with two people we wouldn't have enough points to unlock everything, and I feel really bad for any single player people who have to be very, very careful about what they unlock.
Ultimately, co-op felt rather hollow. After building a few huts and murdering a few dinosaurs with our slingshots it basically felt like there was nothing much else to do except grind exp (so we could unlock more toys), and that got boring real fast. It seems like it was designed more for dedicated servers with PvP.... but I honestly don't understand the appeal of building something, going to bed, and checking back the next day and someone burned it down and murdered you in your sleep so you have to start over (especially considering the above grind which means everyone is going to be a high level and able to stomp your crap in for a loooong time before you can compete).