I have been to MIX twice now, and both times it was FANTASTIC. The view is amazing (we have eaten both inside and outside) and so is the service and food. We had two different waiters and both were so great - really helpful, sense of humour. The sommelier was really helpful and patient choosing wine.
Food-wise: The shrimp cocktail is awesome, and NOT your usual shrimp cocktail (it almost ends up being more like a salad.) The lobster curry sounds crazy but it's fantastic (we ordered one with our entrees, for everyone to share!), and the wagyu beef stew is soooo good - I don't know why they bother giving you a knife, it falls apart. They also do this crazy dessert cocktail that has this foam on top - it's like a passionfruit/peach type thing. So amazing.
It's not the cheapest place to grab dinner, but well worth it. We have so enjoyed our two trips and will definitely be going back. A must, if you're in Vegas.