We enjoyed the concierge service during our last New Year's visit to the world. I think whether it's worth it or not will depend on how late you're out at the parks and how much you plan to be around the hotel.
Our party was somewhat split with two of us spending almost all day every day in the parks, while the other two spent a lot of time around the hotel. It was probably more worth it for the two who stayed in the hotel. Two of us were never in the hotel around lunchtime, so we didn't get to enjoy the buffet then. We were also coming in late from the parks each night, so the buffet was usually cleared away by the time we got in. Your mileage may very though, depending on park hours during the time of your visit.
We enjoyed the breakfast foods, and the quick and easy PS help was nice. However, we probably won't do concierge again until we plan a trip where we intend to do more hotel time and less park time.