Jeff, you may want to add an option to PRSCustomizer that allows the users to easily replace the default Reader fonts. Yes, the customizer comes with its own Cyrillic/Eastern European support, but there are other reasons why one would want to change the default fonts. I for one wanted to replace the default text font with Caecilia, becuse it looks awesome and is faaaar easier on the eyes than Dutch Roman (which is the Reader's default).
What I did was follow instuctions given
here on how one changes a font to something the Reader can use (basically one needs to rename the font on both the file and font level), then replaced the font PRSCustomizer created for me in the sdcard folder.
It would be really nice if PRSCustomizer could have something like "Load personalized font" button, and the program would do all the necessary work of renaming the font and file and placing it in the required folder so it all works with the device. That would also make it easier for people to add their own languages too, so you and porkupan wouldn't have to do it all by yourselves.
Cheers,
Valloric
EDIT: Oh, and just in case anyone does the same thing I did (replaces the default fonts), you have to reload all the books you have on the Reader. That is, delete them, then add them again. If you don't, a few lines of text from the previous page will appear on top of the next page. This is because the book you loaded before the font change was adjusted for the font you previously were using. Deleting and adding the book again solves the problem.