I've been to MIX a few times now. There are a few different sections to MIX so I'll break it down.
The restaurant:
They use to have a Restaurant.com deal so it helped with the steep pricing. The food is pretty good but not memorable.
The lounge/club:
This is not your traditional night club. There is a dinning section, the bar, the outdoors lounge (with a bottle service option of course). There is a DJ but the music is...mixed. I'm not quite sure what genre or timeframe it's from. Not many people dance and the patrons are generally a bit older than the trendy night clubs in town. The bar is a mess. They make some of the drinks "in the back"...I put it in quotes because I don't know why the have to go to the back. I see the alcohol, I see the juices...mmm whatever. Like most nightclubs in Las Vegas, the bartenders are swamped and pressured to turn out drinks quickly. I feel for them on that front. But you don't have to have rude to me when I've patiently waited to be served unlike some other people that push and shove and throw money on the bar. Don't huff and puff at me and stomp around. For this reason, I'm not coming back.
Overall:
+Great view of the strip from here. You can't see as much from the dining room but the lounge is great. Also check out the lounge's restroom! You're in for a surprise!
-There's obviously no cover to get into the lounge from the restaurant but there generally is a cover after 9 or 10pm. There are often people in the lobby passing out discount entry passes but if you stop by the Mlife desk, they might give you complimentary passes. It's not worth it if you're paying to go up to see the view.
+/-No dress code (nothing enforced, but lots preferred)