I travelled with Union Ivkoni the weak before from Thessaloniki to Plovdiv and it was really anoying, the bus was delayed and uncomfortable.
The travel from Burgas to Istanbul was the exact opposite. The bus was completely in time, the seats were comfortable and the service was great. The passangers even got snacks and drinks provided by the operator. It was a real good bus ride.
Autobus Standard z klimatyzacją, Union Ivkoni International , 19 kwi 2022