We stayed 4 nights at the MGM Grand in Nov of 2012. Generally, our stay was very nice and the staff at the hotel was absolutely great. I have stayed at many properties in Las Vegas and would characterize the MGM Grand as a good place for anyone in the 20-39 age group. We got a great deal on a Spa Suite (part of the Grand rennovation) as we typically stay at the resort where we can get the most for our dollars.
Based on the services we used during our stay, I would say that the pros of the MGM Grand are: an active nightlife, many great restaurants, exceptional staff, and a fast valet service. On the other hand, I would say that the downsides to this hotel are: 1) check-in...a 25 minute wait in a long line to check in on a Sunday afternoon (would hate to see what a Friday evening check-in looks like) and 2) some issues with hot water in our suite.
I have now stayed at both MGM Grand and the MGM Signature (non-casino) hotel adjacent to the MGM Grand. In my opinion, the Signature is a better $$ value.