I have used ola cabs many times in Delhi. Not every time but most of the time OLA cab services are satisfactory in terms of timing and driver behaviour.
I have observed that girls in Delhi have been benefited immensely due to OLA Cab services as now it's more easier for them to visit certain places.The best part about cabs is that it gives you a scence of safety . Althogh UBER cabs are also good but comparing OLA and UBER , I personally will prefer OLA as they have more number of cabs.