I started using taxi for sure during feb 2014 I think. From then on till today I booked their service using the Mobile app. Pretty fast I should say as by the time the app identifies the nearest car I already get a call.
Very courteous drivers and very prompt too. No hassles billing and quite transparent. Like the fact that my bill is emailed to me.
I have used them 4 time till today and at various times including a Saturday at 1 Am and I am pretty impressed that they were available at all times.
Hope they maintain this level of service.