If you need a great place to eat late at night at the Mirage besides Carnegie Deli then BLT Burger is the answer.
It has a very nice vibe to it and pretty hip located right next to the entrance going out to the strip and right across from Sugar Factory and Rhum Bar. This location use to be the viewing area for the white tigers when the Mirage opened but it has commercialized into Corporate Las Vegas, removing anything that is free with $$$.
The food here is not cheap but for being on the strip, you'd know this is another touristy restaurant but that didn't stop me from eating here three times when I stayed in the Mirage. Service here was excellent and the burgers were delish! Just ordering a combo with onion rings and a lemonade just adds up to around $30!
If you want to get quicker service without waiting for a table, then I suggest you go straight to the bar area and they can serve you right away, if you can find an open seat.