I just read the reviews from two individual losers and their experience is 100% different from every time I have been to Nevados. Although Mammoth is open year round, they rely on making money during the winter time. In the winter months, It is busy and I mean really busy. If you are planning on going, make a reservation because it is a favorite for the locals all year round.
Here is a little advice, "If you have a reservation and and aren't going to make it in time bacause you wanted to ski longer and then meet friends for drinks, make a later reservation - jackass."
With regards to the decor, the building isn't in the best shape and it is a little old. Keep in mind that you are not eating the building, you are eating the food for the food!
Give Nevados a chance if you haven't been there and you will be glad you did.