There always seems to be a line here, but it moves fairly quickly. They are definitely not afraid to pile on the toppings for you, and will gladly let you add additional salsa (I personally like to add pico de gallo and corn to mine), or fajita veggies. The barbacoa burrito I ordered was a behemoth of a meal, approximately the size of 3 regular looking burritos due to amount of fillings they put in. I'm surprised they could actually wrap the burrito from end to end because it was so large!
Fountain sodas are Coke-based, and there is ample seating.