As someone said before, don't let the looks fool you. The place is unassuming, but the food is amazing. The beef kabab is the best I've had, the adana kebab is tasty also, if you like lamb. The salads and appetizers are to die for, kjopoolu - the eggplant and pepper salad is my favorite. Nick is a very attentive host, if you mention that something looks good he will bring a small tasting plate to your table to try.
There are many options for the vegetarians, last time he grilled an excellent piece of salmon for my friend. The turkish falafel is not my favorite, I prefer the Lebanon falafel so I haven't tasted the falafel at Istambul. The sweets with tea are great to finish the meal off.