Found a unpleasant bug today.
When you start HackedUpReader while already reading something with the Kindle's own reader (for example having a dictionary open) and you press the home button, the main "My Items" screen gets shown and HackedUpReader's windows is put into the background.
Which is bad as you can't get it back and HackedUpReader can't be restarted unless you do a reboot (or kill it from the command line).