I recently traveled a week in Turkey by bus. Here are my experiences:
Metro: Traveld Kapıkule/Edirne-Istanbul, Kapıkule/Edirne-Bursa. Sales Office Experience: . At the Metro Haskovo Counter they speak understandable Turkish and are also very friendly. At the Edirne Counter (Metro Volkan) personal was very stressed and unfriendly. Avoid travelling to or from Edirne with Metro anyway, the bus stops somewhere on the highway, if it stops (In my case it didn’t which resulted in some adventourus hitchhiking to Haskovo).
Ulusoy: Traveled Bursa-Ankara. Sales Office Bursa was friendly, but the Conductor was not very friendly and threw his garbage out into the nature. Ulusoy uses its own otogar in Ankara, which is not really convenient.
Kamil Koc: Traveled Ankara-Canakkale. Not the fastes but the most luxurious bus with personal TV stations and a big plus for the head phones.
Canakkale Truva/Soma Seyahat: Traveled Canakkale-Edirne: Unprofessional counter personal. Suicidal driver. I am lucky i survived.