I've been here twice over the past year and have been impressed both times.
Its semi-fast food. Where you line up and order/pay at the cash, then wait till they call your number to pick up your food at the counter. Then seat yourself.
While there is plenty of seating, this place is packed for dinner on the weekends (not sure about other times).
The food is really fresh, the portions are huge, real plates/cutlery, they will give you a jug of water if you want.
I tasted the following:
Chicken Tikka Kabob: moist, super flavourful chicken
Sultani Kabob: a great choice since you get two types of meat (Barg Kabob and Kofta Kabob). The Barg was really tender!!
Firnee: a pudding dessert, quite good.
I cannot comment on the authenticity of the Afghan food. But everyone eating here seemed to be of middle eastern decent... so that means its legit right?? that's what i'm going with...