I am using Airtel Broadband WiFi since October 2011 and have experienced almost nil downtime, except once or twice. In case of problems, the call centre was swift and resolved the issue within 4 working hours. The speed is excellent and extremely reliable.
Only thing is there is no Data Usage Meter. Or maybe I don’t know how to find/use it. I am on Unlimited Plan where first 10GB is at 4mbps, and after that its 256kbps. But I don’t really know how Airtel measures data usage.
I recommend this service. Simply wonderful, go for it.