I got a Polish SIM card for my iPhone today. I went with Play at the recommendation of a Polish friend. The Starter Kit was 19 zl ($6.50).
The man at the Play store popped it in for me and it worked. It simply worked. Phone, data, done. Not like the configuration needed in Central America.
But is that a result of the Polish system or being on iOS7 instead of iOS6 or having an iPhone 4s instead of 3gs? I guess I have to return to Central America to find out.