John, were I work we have about 100 employees on the mifi's that are used in six of the counties we are in. Service is OK, but changes often based on weather, etc.... Some employees can have it work one week and be in the same place the following week and have it not work. The best speed we have ever received was 2mb down with 3g, upload speeds are normally between 384-512K. Verizon just turned up 4G in one area and our tests show 12mb down, however upload speeds are still poor, still around 512-768K. latency is still an issue with cellular, doubt it is anywhere near as bad at satellite, but it is there. You may want to check to see if they have an unlimited plan for business customers, all of our cards are on an unlimited plan because we are a business customer, they do not advertise it, but I believe you can still get it. Another option you could do as handiman suggested and see if your neighbor would let you setup a connection off of his charter. 800 feet is not far at all and there is good equipment that can go through trees, I can get you some info on the equipment if thats something your interested in.
Paul