OK, here is a very brief guide to changing the font for ALL EPUBs even DRM'd ones, except those with embedded fonts, on the new Sony readers:
1. Download and flash the "Boroda" firmware from the Russian site. Here is the Google Translate link:
http://translate.google.com/translat...a3&sl=ru&tl=en
DO THIS AT YOUR OWN RISK
2. The Russian firmware will automatically replace the default Sony font with the Droid font. If that makes you happy, you're done.
3. If you want to use another font, the Russian firmware creates a folder called 'epub' on the READER volume of your device. You can browse to it in the file browser of your choice when the reader is connected to your PC.
4. The 'epub' folder contains three .css files. called 'userstyle', 'userstyle.dflt', and 'userstyle.droid'. 'Userstyle.css' is the one the reader uses to pick the default font. The other two are for the Sony default font and the Droid font respectively.
5. The 'epub' folder also contains a 'FONT' folder. Create a subdirectory under this folder and copy the True Type or Open type fonts you want to use to it.
6. Edit the 'Userstyle.css' file with any text editor to point to your preferred font in the folder you just created. (you might want to copy the original file first). The .css file itself is pretty self-explanatory, but jswinden's guide covers how it works.
7. Enjoy your new font.
My reader is currently using Cambria.
The hardest part is flashing the firmware, and that is really easy if you follow the directions. Don't do this if you are uncomfortable with any of the steps.