I got one of Sprint's 3G/4G usb modems to test and this is my experience:
If wireless unlimited data, 4G only with Sprint, worked better than 3G in my area, I would dump Road Runner in favor of the Sprint 4G plan internet service in my home. However, 4G is less than half the speed at my home of 3G, and if anyone investigates Sprint's current offerings, 4G is unlimited, 3G is not.
So there is a caveat to the "unlimited" plan that the article does not mention, and that caveat is that 3G is not unlimited, where 4G is, and with Sprint, 4G coverage is not as good as 3G. Therefore, Sprint's "unlimited" service has some built-in limits to it that some may be not aware of.
So, if you are expecting "unlimited" with Sprint, make sure that you are in a solid 4G reception area; otherwise, their 3G service is subject to caps, and their overage charge is $0.05 / MB - that's MegaByte, Yes, MegaByte meaning $50 per GB - way more than other carriers are charging.