Straight Talk?

Hey everyone. I'm currently with AT&T for my cellular service right now, but I absolutely hate their pricing. I recently noticed that T-Mobile's plans are much more cheaper than AT&T. If I could, I would switch to them. However, their network is horrible in my area. AT&T has 3G service everywhere that I go. According to T-Mobile's coverage map, they'll only have 3G service at a couple of the places that I routinely visit. I was ranting about my dilemma one day in the comments, and someone suggested that I check out Straight Talk.

I recently took a look at their site, and it looks a bit too good to be true. According to them, I can still use AT&T's network, while getting unlimited talk, text, and data for only $45 a month, without a contract. There has to be some kind of catch or downside here that I'm just not aware of.

Does anyone have any information about Straight Talk? Is it really as good as it sounds? Any help would be appreciated. Thanks!