I'd love to give MGM more than 3 stars but that's an average for the 8+ years I've stayed here. It's either hit or miss with the rooms/customer service. Our most recent visit - NYE weekend was overall good. We recently upgraded to the Gold card with MLife so we got the $20/day valet parking for free which was great! First impressions with the front desk are usually pretty good - not so much this time. We got in line for the Gold members, etc. all excited and were told to go to the other line by a rude lady since we booked on credit card points instead of directly through them! I'll also add - there was no one behind us so no reason to kick us out of line but our next lady made it up to us and upgraded us for a small fee to a strip view stay well room. We were early so we went into the stay well lounge - which was pretty unimpressive but it was a smoke free place to relax for a bit. The room was nice, was probably one of the cleanest we had. (Last one had mold, hair everywhere, smelled...I could go on and on).
Whatever you do, don't stay in a west wing room - always stay in the grand tower because they are much nicer/updated rooms. Sign up for the card and use it because they do give you good deals sometimes. Definitely play MyVegas before going because they have free stuff on there all the time (monorail, buffets, freeplay, etc.)
Overall a great place, we try other hotels but keep coming back - we know where everything is and there is so much to do in this area. They certainly have some things to work on but for the most part it's a great hotel.