jinsprings, you are correct. As I mentioned, Sprint started what was known as PCS. It was designed around the metro areas and the interstates. So yes, if you're driving cross country, and you're on the interstates, there's a very good chance you'll do quite fine with sprint. If you get off the beaten path, that's another issue. So, if you look at a sprint coverage map, and compare it to a verizon or ATT coverage map, you'll see quite a difference. Sprint primarily is along major interstates and cities/towns. Verizon and ATT also extends out to the other areas also. Now mind you, Colorado, as well as surrounding states, is very mountainous, and there's certain areas where NO CELL PHONE WORKS. But when you get out of a major town/city, and off of a major interstate, Verizon/ATT are much more likely to work. Here's sprint's coverage of Colorado.
And verizon's for the same basic area:
AT&T is similar to Verizon, except their DATA capabilities change. Their 3g data network varies in speed, depending on where you are. e.g. Denver or colorado springs will be faster than on the interstate some place. And some places, it's even faster than Verizon. Verizon on the other hand, has their full 3g EVERYPLACE that their voice service works. So, the ATT map is harder to read, because they use like 5 shades of colors. But it's about the same as verizon.
Anyway, nothing wrong with sprint. But if you're really into exploring, getting out and seeing the world, not always staying in the cities and along major interstates, Sprint might not be best for you. But if that's where you spend all your travels, then there's nothing wrong with sprint.