We had crab legs at CR in May and thought the portion size (like most of what you get at Disney) was very good. And we're not small eaters, by any means, lol. They cut them open for you (rather than having you crack them at the table). While some find that convenient, I thought they were actually harder to get the meat out that way (and they didn't give you little forks to help with the job). But, they were yummy!
Also, do they let you substitute anything else for that corn stuff? DS13 loves crab legs and will surely order this when we dine here, but noway will he eat the corn mixture and I don't think just crab will do the trick.