I've come here a number of times and I would say it's decent Mexican food (for Pittsburgh).
Atmosphere - they recently remodeled and the decor is really nice. Warm and inviting. The bar area has flat screens with sports on. I love the view of Market Square.
Service - Get here before the lunch rush and you should be fine. It gets a little slow during the lunch hour. The staff are quite friendly though.
Food - as I said, it's decent Mexican food. The lunch combo is a good meal and not too large. They do charge for chips & salsa. The tortilla soup has a nice kick to it.