I have been using airtel as my datacard sim. I have an USB data card from micromax. I got excited about BSNL unlimited plan in which you can keep browsing at lower speeds even after you use up the quota.
But It was just an eyewash. Even when you are within your quota the speed and connection is pathetic compared to airtel. On an average I have to wait 10 secs more( when I am in an 3G connection) for a website to load in BSNL compared to airtel.
Now that BSNL sim is just lying around some where in my house playing its part as my household junk and I am back using airtel.