The only ISP that's using 4G (or WiMax, I forget) for home use is Clear Wire. Otherwise, if you're not going to consume a lot of data online (and 3GB-5GB is easily consumable if you visit say YouTube or something), then sure, a mobile hotspot would work.
I'm also very weary of wireless internet anyway. I've had nothing but reliability issues when I stayed at a place with it.
I really should have put this in the Network Nook portion, as I'm primarily interested in the home networking capability / possibility involved, I already have a good handle on the rest of it.
AT&T provides the 3G/4G data plan, and is the ISP in this scenario.
Don't confuse "Wireless" or "Wi-Fi" (802.11) with 3G or 4G. Wireless & Wi-Fi are local short range solutions. I'm talking 20 - 50 yards without obstruction for most home based solutions, and some businesses with "Wi-Fi" are using those exact same home based solutions. While there are some business based solutions (like some of those used in AT&T's Wi-Fi HotSpots) which can extend that range to hundreds of yards omni-directionally, and up to a few miles uni-directionally, but are still subject to obstruction issues. Basically, you need to be close to the source to get good signal, especially if you're inside of a structure.
3G / 4G is a long distance solution. 3G & 4G are carried over the same digital signal as your cell phone voice communication signal & are bounced by local cell towers just as your voice signal is. Just as with your voice signals, the data signals (3G or 4G) pass right through most obstructions. I usually have 3-4 bars on 3G inside my house (tin roof), at my best friends house, I usually have 4-5 bars on 4G (shingled roof), at least according to my new iPad.
This is also why Wi-Fi is "free" & unlimited (free as in, there's no additional cost to me as I'm using it, or any additional cost to me if I exceed my download limit)
and 3G / 4G is not. It costs a lot of money to send data to a satellite then back to Earth & that's not counting the cost of the satellite, or the cost to put it & keep it in orbit. Whereas Wi-Fi hotspots are hard-wired directly to an infrastructure that was paid for decades ago (like your cable or DSL internet) and has virtually no new costs involved beyond the equipment itself, and occasional maintenance.