Its a good service to be used. The only bad expirience (rather worst), I have had is when they were actually facing some system problem at their end and there was no intimation to me about the cancellation of my cab booked to reach the airport.
I did receive my booking no. however there was no intimation mesg which they send 20 mins before the time you have given for pickup, and I called them up and they said no CAB service is available since the systems are down. It was a rainy day and I had to run to get hold of a rickshaw/taxi to reach the airport as I had some heavy bags with me.
Else wise they have been quite professional and the cars have been neat and drivers well spoken, do have the sense of directions while driving. So to summarise it has been a quite journey till date of this review been written, via the meru cab.