The value for the money is great at the Mirage. You get great service, nice decor, and the rooms have recently been renovated (so they are no longer absolutely crappy). The common areas are great.
Only one word of caution: Skip the restaurants here, and stay away from the buffet unless you enjoy food poisoning.
Absolute must: Hang out at the Revolution Bar. It's a great place to be, and the bartenders are friendly, courteous, and well-versed in all things drink-related.