There were a few hiccups getting to the starting line with our complicated itinerary, such as not warning us when they were taking large payments from our credit card, and misinterpreting our requirements, but they have very good service available by phone and email (and face-to-face), and we ironed those out and got there.
The tour itself went well with very few hiccups. Transfers and guides were very good.
Having said this, they sub-contracted the majority of the tour to another company, Acetes, and it was those fellows that kept us on track and fixed those minor problems. Hands down, Acetes were fantastic!
We had a great tour and the guides were very patient with us (family party, youngest of age 3 and eldest with mobility restrictions). For Istanbul I would use TTC again. If it's out of Istanbul you're after, I highly recommend Acetes (in particular their Kusadasi office).