Geez, nobody else responded to you? Sorry about that. That probably means Sprint has no plans of improving service in many places at all. Sorry.

You're only 7 miles outside the coverage area. Do you live and work in that zip? If you actually work in the city you could try the America plan that Sprint offers. Things could be worse...you could live in zip code 59904.

One step at a time. Up to this point in time Sprint has built their own network completely from the ground up without buying their way into the industry. Towers are expensive to build and take time to get through all of the regulatory processes and the tree huggers who think that a wireless tower will kill of the endangered slugs.
Other carriers have been building out since 1985. Sprint and T-Mobile have only been in the wireless game for less than 10 years.
It is not reasonable to expect the same buildout in less than half the time as the incumbent cellular carriers. For all that they do cover they have done a great job.