Papa Hassan's is pretty mediocre in my opinion. I know a lot of people who love it, and it's very convenient and cheap if you go to Chapman University. The best thing there is the falafal, which seems pretty hard to mess up.
I think there hummus is too lemony but their grape leave (dolmas) are ok.
I had some meat sandwich there...I forget which meat. But it was salty and overcooked.
But the servers are really nice and for lunch it's a good deal. I think the chicken is pretty good if you need a safe bet meal.
They give you pita and butter with your meal, but hummus or any other dip will cost you.
Lentil soup is also a good dish there.