Considering the price point of the MGM itself and the prices of other restaurants inside and around the MGM, I feel that the MGM buffet is the best value for your money. I spent $15 on some chips and (nonalcoholic) drinks in the hotel essentials shop, so for only $15 more you can have all the food you can eat.
The selection at this buffet obviously isn't anything close to places like Bacchanal or the Wynn buffet, but for $29.99 I think there are several solid options that make it a good spot for dinner if you'd rather not leave the hotel. There are (dungeness) crab legs and prime rib every night, and a reasonable variety of cuisines (Asian, Italian etc.) to choose from. The dessert station includes a soft serve machine and sundae bar. Drinks are self-serve, which is neat because they have the special Coke dispenser that mixes flavors.
Nothing incredible or fancy, but you'll definitely leave with full stomachs and not-entirely-empty wallets.