This is not isolated incident in Bangalore.I am facing the same problem for last two years.I stay in Pay Layout, Bangalore. When BESCOM power supply is available, my mobile shows full signal. Good, my mobile is attached to nearest cell site.but, when there is power cut in the area, my mobile shows really weak singal. seems like Airtel's cell cite nearer to my home doesn't have power backup. so at the time of power failure my mobile has to find Airtel's another tower and getting attached to a tower which is not intended to serve my area and hence signal strength is low.another issue that if power fails while I am on a call, my call fails too.Yes, Airtel is best in Karnataka. I donot have any issue other than this. but this issue is not something that I can ingnore. the other day when I was attending a meeting from home, I had to join conf call multiple times when there were multiple power failures in an hours time in my area.Again, this is not may not be the case everywhere in Bangalore.So, if you are evaluating possibility to go with Airtel, buy a prepaid sim try it at your home and office/business and then go for full pledged connection only if you didn't find any issues after trying it for good amount of time.I donot think Airtel prepaid costs much(I am not sure about signup costs).Airtel is worth trying. in my last four years in bangalore, I have evaluated Reliance and Vodafone for my second mobile connection(for my family). what I can tell is Reliance and Vodafone sucks in Bangalore.