I think this is the key here. If you are going overseas with it you will get hit by some hefty charges.
It is also worth noting that Sprint will cap your data while you roam. I think I remember reading 200mb for the month, but don't quote me on that. I am not certain at all what their policy is on voice and texts.
I think it needs to be said again... if you are in the U.S. and a U.S. based customer, there is no roaming, so it does not matter. If you leave the country, **** hits the fan.