I've updated my Pocketbook 302 with the 15.2 (1-jun-2010) firmware. After restarting the device the firmware version (in the about screen) showed the correct version.
However after the next powerdown/powerup the device went into a continuous reboot cycle. I.e. after a few seconds in the main screen the reader restarts itself.
I've managed to reinstall a 15.1 firmware after which the device acts normally again. I'm hoping the next firmware release will be more stable.