I have a airtel 4g dongle and I am using it from the past 7months. You will be quite lucky if you have 4g range in your area. Well ., when compared to other networks airtel gives the best service and speed. At sometimes I may get as much as 26 mbps and sometimes may go as low as 0.2 mbps.
I would recommend that u go for it, until a new network operator gets 4g in your area.