I've seen many concerts here and last night, I watched Madonna. The ushers are always pleasant making my concert-watching experience a delight every time. Last night some of them were dancing before the concert started - they were so cute and got me pumped up. It was a sold-out show but with no hassles, no chaos.
Even the stalls to buy merchandise from were well-organized. The only thing that was holding up the line were people who don't really know what they want to get and what size they wear - seriously? After standing in line for 20+ minutes, you should have all that figured out.
Parking is alright if you get there a few hours before a concert. Getting out of the parking lot after can take a lot of time and patience. There are a lot of good restaurant options at MGM before a concert and bars after the concert.
Overall, my experience at MGM Grand Arena has consistently been positive. They do such a great job and I wish all concert venues would be as organized.