I've had T-Mobile since 2005 - mainly got it because my Minneapolis bro recommended it, and more so due to T-Mobile having huge international coverage and I planned to travel a bit, also have many contacts in other countries as well, and at the time no one else offered international anything. 

I signed up online and they assigned me a number out of Brainerd where they have a tower, so a few people weird out at that, as it's technically long-distance for some to call who call from landlines. Oh well.

As far as the contract, mine ended in 2007 and I only have a very basic mobile phone - old skool Nokia flip-fone (no smartphone) and it runs $54.99/mo ($15 of that is unlimited messaging due to all the text fiends in my life or I'd ditch that extra cost) $63.49/mo total with taxes and fees.

A Duluth friend had his T-Mobile pulled same as Rhetoricguy in 2010. I thought mine would be pulled too, but never has. Perhaps due to the number being assigned out of the Brainerd area? I dunno. I wasn't gonna ask and alert them.

I never have a problem with local coverage, and in fact have had coverage in many locations others did not and would borrow my mobile or just be amazed that I had service. Last year I even had great coverage in a small town in rural Guatemala. Parts of NZ were a challenge though.

T-Mobile uses/roams the local towers, but as I understand, have none of their own in Duluth and won't. Currently my screen reads T-Mobile as my operator, and when I use the menu to manually search/choose an operator, it currently shows two choices: T-Mobile or Cingular. I've seen others as well, depending on where I am.

Can't speak to the Ashland coverage as I've not gone up that way since having T-Mobile. This tower search map shows nothing for that area, but it'd most-likely pick up other networks depending on their coverage.
 
Wanna take me for a road trip and find out?