I used ola for the first time when I went to Delhi in 2013, since then I have always been using them for all my cab requirement.
The app is very easy to download and very easy to book a cab. The variety of options of cabs is what I like the most, you can book a mini, sedan, prime etc through this.
In addition I get good offers also which is very nice. If I want a cab I always prefer ola instead of other cabs since it has a panic button in the car so that in case of emergency one can use it.