I have tried to use MakeMyTrip on a couple of instances and there had been a terrible goof-up of customer service. The first one was around an year when I booked a vacation with my wife to Manali via New Delhi. The customer service who booked had several mistakes in the ticket a few were:
1) Spelling of my wife was incorrect on the airlines itinerary
2) The hotel date itself was wrong. I had to make several calls to the hotel and MMT besides on the day of journey too to ensure things were in place.
3) The Manali bus pickup at New Delhi was again mentioned at a wrong location. When we called MMT the customer service rudely replied that they can not help in contacting bus operator because their responsibility ends by booking a ticket.
The second goof-up with MMT was when I tried to book a domestic flight from Mumbai to Chennai a couple of months back. Even there the booking payment gateway tripped down. Had a long ordeal to get the payment reinstated back to the source account.
I had another experience with MMT cab booking. Though MMT accepts payment via website and books a cab like from Mumbai to Thane/Pune etc, more often the cab operator calls a day later and asks us to pay for the return trip also. So we end up paying twice the charges other than what we paid online through MakeMyTrip. This hidden charge is surreptitiously hidden in the fine prints of MMT terms of service.