I booked this through Living Social and had a lot of trouble learning about it through MGM's site but we had an amazing experience here. We stayed at MGM because of the UFC fights at the Grand Garden Arena and we didn't even know at the time of booking that there was an indoor walkway from LSI to MGM, which if you're in MGM and following the signs is marked "Signature" when you're in the MGM Casino.
I loved that the parking was private valet, the room, bathroom and living room was gorgeous and the service we got from the staff was fantastic. We were in the second of the three tours behind MGM, not sure if LSI is in any of the other two but I do know that the Signature is in one of them.
The only cons that I have are that because our room did not have a door separating the foyer from the bedroom (there's a small hallway) whenever someone was loud outside our room we could hear it pretty clearly. Also was had some trouble on MGM's site figuring out where exactly the entrance and everything was, what exactly was in the room but the Yelp reviews set me straight. One last thing, as great as it was for there to be a DVD player in our room, the TV remote didn't seem to sync with the DVD player. No biggie since walking up and pushing the buttons old school style isn't physically difficult.