In summery: good quality, poor quantity - limited value.
Naf naf has some place for improvement - I think the quality of food is great - but the quantity decreases the overall value. I have had shwarma all around the world - and typically they fill the pita with at least 3/4 of the way - with Naf Naf, my pita is typically half way empty, and the limiting factor is the quantity of meat (which is understandable from a business/profit perspective but as a consumer not so great). Also, If you want to supplement with fries or other additions - it becomes even more expensive - which again decreases the overall value. I have been to 2 chicago Naf Naf locations and felt they were a bit more generous (perhaps they had a bit more competition).