The bus ride from Ankara to Istanbul is about 50YTL ~ roughly equal to about 30US dollars. For that price you get a non-stop trip for a ride about the distance from New York to Washington, DC. The leather seats are wide and comfortable and you get more than enough leg room, even for taller passengers. They serve a variety of non-alcoholic drinks throughout the journey (also included in your ticket fare) and there is dinner and snacks along the way. All from the comfort of your window side seat.
A beautiful trip if you go during the day through foggy mountains of northwestern Turkey. Those of you heading to the airport will find free shuttle service in both Ankara and Istanbul. The free wireless Internet (yes on the bus!) will let you email, MSN, and read L’avant Poste during your ride.