For individual use, a jetpack-style hotspot device is great, and true pay as you go would be ideal, especially for those that are not under contract, use pre-pay phones, or have a work phone and don't need an individual line. My only concern about a higher up-front cost is the amount of usage vs. the life cycle of the technology. At a low usage point, it makes more financial sense to use the hotspot feature on your smartphone.
Now, for commercial applications, such as a small construction business, or someone who works in varied remote locations, or for rural home usage, where running a line to the house is cost-prohibitive, a 4G router like this would be a great solution. I'd still prefer true pre-paid, but an unlimited month-to-month plan wouldn't be major heartburn for this usage.
Hell, a 4G router like this, plus a good antenna for local channels, and I might be able to kill off direcTV at the hunting camp...