I have Tata Voltas AC last 4 years, I have fantastic experience from the same, there is no service issue, excellent cooling, easy operate, excellent mechanism. Service engineer is supporting well. it is superbly silent despite being a window AC.
Last year I was having problem understanding few of the function in remote, and the technician called me up just a day after I filed an request with the Voltas call center.So finally I am fully satisfied.