A friend of mine is IT Director for one of the largest counties in the USA. He has had his laptop on a Sprint aircard for over ten years. Back when he first got his, he benchmarked just shy of DSL speeds (over 100 mbps) and that was long before any "2G, 3G, etc.). Feel free to ask the sales person at Sprint what the datarate would be in your area. S/he's going to tell you "well there are no minimums promised, but in your area we have "x-G" and that usually runs from this speed to that speed.
The thing more then speed is connectivity. There are still some dead zones in the land of cell phones. That's the only problem I have seen people have with wireless broadband cards. As long as you get a strong cellular signal, it should work great for a redundant data connection in case your system, or the building it's in, blows up.
Most also have a 30 or 60 day period where you can test it and return it if it does not fit the intended purpose. Surprisingly I have seen people get out of contracts when they move to a place where cell phones just don't work which is common on islands away from populated areas.