I have been an Orange user for the past one year.
My experience about it has been absoutely fantastic. Earlier I was on prepaid where I did face some difficulties but switching on to post paid helped me a lot. The service and response that they gave was faster.
Signal and reception wise both prepaid and postpaid are very good. Postpaid the slightly better. Reception inside the train coompartment is excellent and there is no disturbance, something which cannot be found on other services.
Although it needs to be added that there are certain places where u will not get any signal, even inside Mumbai, e.g Vashi Bridge.
Quite recently it has come to my notice that service to the prepaid card users thas also improved drastically and is on par with the postpaid users.
All that a user has to do is send an email to their customer service and orange will themselves call you back and resolve your complaint.
Also billing statements provided are very easy to understand and with easy break-up of costs charged.