We used the dining plan a couple of weeks ago, and yes, there was too much food, but we felt that we had to try to eat all of what we ordered. I would be much more picky the next time, but it was so easy to get caught up in the "free-ness" of the whole thing.
One thing to be careful of is that if you order anything not covered by the dining plan (such as cocktails) you will be given two receipts, one with the dining plan only items that you must sign for, and one with the extras that you will need to pay for. We tipped on the extra items based on their price, but after a couple of meals we noticed that a 15% tip was already added to that bill so we were double tipping for the extra items. We didn't begrudge the extra money, but would have liked knowing ahead of time.
Also we were shocked by how booked up the table service restaurants were and you will need to make reservations in advance. We are normally spur of the moment people but after trying to walk up to all four restaurants in MGM at 4pm and being turned away we found it necessary to be a bit more planned than usual. We had some great meals, though.
Enjoy!
Tink