I have now had 4 Mi Fi's since August 2011.
The first one lasted less than 3 months (It was brand new) Spent half hour on the phone troubleshooting.
I was sent a "certified preowned like new"-it lasted less that 4 months when a connection came loose-I was sent another "certified preowned like new".
This one did not work-spent a half hour on the phone troubleshooting-paid $12.99 to have another one shipped over night which arrived 3 days later. This one (another ceritified preowned like new)did not work either-I spent an hour on the phone troubleshooting it- I asked to be released from my contract or sent a new one- I was told that they would have to put in a "work order" and would call me in 2 or 3 days- I asked how much time I would have to spend on the phone this time and was not given an answer.
DO NOT BUY ONE OF THESE. (they also suddedly turn off)