Holsteins is a good option if you're in/near the Cosmopolitan and looking for a more casual place to sit down and eat. They have a pretty large menu with a number of different burgers, sandwiches, alcoholic milkshakes, and other fun versions of bar food.
The food here was expensive for what it was (not a surprise, it's Vegas) and it was good, but I have definitely had a better burger. I tried the new England Turkey Burger and the toppings were great (frisee, cranberry mayo, and stuffing), but the burger itself was weird... almost more like sausage than ground turkey?
The sweet potato fries were really good and I loved the truffle popcorn that they leave on the tables to snack on before your meal.
Don't come here if you're in a hurry to catch a show-- the service is sloooow even when the place isn't that busy.