I bought 4G modem + router in August 2012 after getting a demo at my house.
Airtel 4G is the most reliable internet connection I have used till date compared to all wired/wireless connections like Tata photon, BSNL and Tikona.
Airtel broadband was good but I have faced occasional down time with that too.
The 4G router is always on and there was never a downtime. The signal is only two bars on router but I get around 6 - 8 Mbps speed. We need to find the right spot to place this thing to get reliable fast connection.
After using it for 1.5 years, the router is now showing some problems connecting. I have to power off router and wait for 30 seconds, remove sim, put it back then power it on to get it working again! At times I do a reset to factory settings.
Pros:
Fast and reliable connection
No billing issues till now.
Cons:
Expensive(5k for router in 2012)
Wifi signal is poor
router HW issues started after 1.5 years.
Airtel does not supply the antennas that can be connected to router. These are not available in India.
Not good for roaming.
Buy this only after getting a demo at your house. If you plan to buy dongle go for the one that can switch to 3g if there is no 4G signal. The router I use, supports only 4G.