With Ting, you can sign up with either CDMA or GMA coverage. We switched (from Verizon) earlier this year, and had to go with CDMA for our local area. CDMA uses the Sprint network. In our local area (in Alabama), it works great. We've traveled to Chattanooga and had fine coverage there too, but can't comment otherwise for TN or GA. But, we drove to visit family in the upper midwest and had very little coverage when we were on the road (no data, and questionable text...), and poor coverage at our destination (e.g., could only receive some text messages, iffy access to data, etc.).
I think it is not great for rural areas, but it is so cheap that we just deal with it, since it works great for the areas we are in 90% of our time. However, I have heard GMA has better coverage--we just couldn't get GMA in our location.