We had a Sprint aircard for the past 6 years. It normally works fine except when we are in some remote areas. We are in the process of switching over to Verizon as I type this. We purchased a refurbished Pantech UML 290 aircard from the 3Gstore for $59 plus $10 for a sim card. Then we activated it on a month to month basis (i.e. no contract) directly with Verizon under their Share Everything Data plan. $50 for the device and 4G of data. With the Share Everything plan, we can increase and decrease our plan each and every month depending upon our needs. Our usage depends upon whether we are in an area that has good coverage or if we are in a campground that includes good wifi coverage.
We decided to purchase through the 3Gstore because I value their advice as to which device will work with our roof mounted antenna (purchased from them too) plus not having a contract was attractive too. We did have to pay a $35 one time activation fee to Verizon but I believe that would be applicable even if you purchased your device from them directly.