I enjoy Orient Express primarily for its large portions, cheap prices, and wide array of vegetarian options. Other Chinese restaurants in Pittsburgh (and elsewhere) have a much more limited selection of vegetarian in my experience.
Their service might be brusque, but it's incredibly fast, and when I go there, I'm not looking for a fine-dining experience. I usually get take-out, and it takes 10 minutes or less (I often wonder how they make my food so quickly).