I have used makemy trip to book bus tickets, train tickets, hotel bookings and of course air bookings. In short most of their offerings. Along with tedbuss, makemy trip was one of the earliest to jump onto the bus ticket wagon. In terms of comparison, it is the same as any other travel site - yatra, cleartrip, ibibo etc. I have not had any problems in booking from their site, so I dont knoww about the customer service. hotels that I have booked have been good and value for money, over all the web interface is simple and user friendly and occasionally, the air fares here are marginaally cheaper.
I would recommend makemytrip , but in the same vein as yatra and cleartrip. Makemy trip offers a co branded credit card which I dont use, but which frequent travelers may find useful.