I've tried to convert my Inca Empire savegame. All in all the results are good, however there is a couple of things primarily related to culture and pop conversion I want to mention.
My Inca Empire become Bolivia and gets the following cultures: Spanish, Quechua, Aimara and Amazonian.
My POPs become: South Andean in all of the former "main land" Inca Empire, North Andean in all of my colonies and Maja in the part of my empire that belonged to the Aztec Empire until I conquered them in 1450-1500. Plus of course all number of small minorities across the board.
Now shouldn't all of a surviving pagan Inca Empires POPs be Quechua? Or at least South Andean?
Shouldn't I have South Andean culture if all of my POPs become South Andean? Why do I gain Spanish culture?
Why isn't the POPs in my colonies the same culture as the POPs in my main land?
Perhaps some if not all of the former Aztec civilization should have embraced my culture by now? I know it is properly very difficult to model, but couldn't we at least have the nobles in conquered territory be the same culture as the country they are in?
All this aside though the POP converter rocks!