We recently visited Bayside for a late breakfast, early lunch. The food was a mixture of both, so I can only assume they were in the process of changing over. The line wasnt bad and I liked the electronic payment kiosks.
I was unimpressed with the selection of food, but soldiered on nonetheless. I had pizza, flank steak, biscuits and gravy and chilaquiles. The pizza and flank steak were good, everything else was just, ehh.
This leads me to believe that the lunch and dinner selection may be better, but that is only an assumption. The service was okay, our waiter never came back to our table after bringing us our first round of drinks. As good as most Vegas buffets are, I expected more from the Mandalay Bay.