As of February 11, 2014, there is no problem at all. I have Ubuntu 13.04 (in one partition) with the latest updates and it's very simple and easy to connect. Just plugin the Airtel 4G LTE dongle and click on the network manager icon in the panel at top right. You should see the modem detected and an option to connect to new mobile broadband network under the Mobile Broadband section. Click on it and follow through the prompts. Select India, Airtel and airtelgprs.com, click finish and you are done.
I cannot recreate the screen-shot as my connection is setup now, but the screen-shot below will give you an idea of where to go.
Note: Do not use the connection manager from Airtel. It has security issues. If the connection manager is already installed, open terminal and uninstall it as below: