Dunno: I always download English versions habitually, and I did the same with the Witcher. But since I'm Polish, and this is a Polish game based on a Polish novel I figured I might give the original version a try. Have anyone else played both versions and has any comparison? Which one is better?
I'm pretty sure that all the languages are included in the download, so you are free to try both once the game is installed. The language choice you picked when downloading is the INSTALLER language, not the game language. You should be able to select from a bunch of different languages and subtitle options once you run the game (this is why the installer is so big).
I'm an English speaker but I found the Polish voices to be MUCH better than the English voices. Perhaps a Polish speaker would not like them as much, but the English voices are really bad. I played in Polish with English subtitles.
If you play the Witcher 2 at some point, the English voices are much better. But I still preferred the Polish voices, especially for Geralt. I didn't like the actor who played him in English.