Pros of hotel: Check in staff was very friendly & ...

Pros of hotel: Check in staff was very friendly & helpful, wish I had gotten her name.
Our suite was perfect...extremely clean and modern, very spacious. Fitness area looked well-equipped, but we didn't use it during our stay. Indoor pool was on the small side, but also handicapped accessible, so bonus points for that.

Cons of hotel: Check out staff was horribly rude (early hours of 1/5/2020), wish I had gotten her name. If you go and there is a young woman with blue hair at the desk, ask for someone else to assist you.
We had a problem in the room (loud mechanical noises that made it impossible to sleep) that required maintenance and the previously-mentioned staff implied we were lying and thought it was funny that we had to leave at 3:30 a.m. (or stay in the suite with a nonstop noise like something metal was stuck in a fan) because she "couldn't do" an official check in/check out at that hour.

Pros of casino area: Many different shopping and dining options for all guests. Friendly staff. Quality live entertainment.

Cons of casino area: There is no physical separation between the smoking areas and the (very small) non-smoking areas. You will reek of smoke after a few minutes, whether or not you are a smoker.

Bottom line: highly recommend Mohegan Sun for the hotel experience (especially if you don't have to deal with the blue-haired chick) and any non-gaming activities.