I am using Vodafone sim card since 2009 and as I am using their service from a very long time you can understand I am a happy customer of Vodafone. I have not faced any issue with their service yet, they are providing better call rates, calling plan, data plan than other service providers with the good networks in reasonable price.
I have found only one problem or you can say drawback in their service or plan in these 6 years that is their data plans has become very expensive in last from last 1 year. Till 2013 I got data pack plans in very good price and speed was awesome, but now days their service is good but net pack plan is too expensive. I wish they will reduce them soon.