I stayed here the same weekend as the Mosley-Mayweather fight, and it was taking place at the MGM during our little bachelorette. The lobby/casino was a party in itself with crowds of random people just hanging out. During such big events it will take a while to catch a cab out of here so just try to plan ahead when you're trying to get around.
As far a mammoth-sized hotels are concerned everything was as to be expected. A huge expansive casino-lobby-shopping-dining area that requires a good long hike just to get anywhere. The rooms are spacious and the beds were super soft an comfortable.
The thing that made this hotel a bit nicer was the staff. Every single person I talked to knew their stuff.
When I asked the girl at the concierge desk about getting to Mandalay Bay she gave me a few different options and knew that walking was not the best option for 14 women wearing stilettos. The housekeeping woman on our floor said hello to us with a smile. The random maintenance guy who saw me walking down the hall with a bucket didn't even need to be asked for directions, he just pointed me in the direction of the ice machines.
It's those little personal service experiences that made my stay there worth repeating.