I don't know if this app is still being worked on, but I have some bugs reports/feature suggestions:

• The prompt to save would look neater if it appeared before closing the window. This would also allow the user to click outside the dialogue box to not quit after all
• I believe Maemo style guide says that the "Set value" menu item shouldn't have "..." after it
• The "Copy to Clipboard" menu item shouldn't have second capital C
• Set value text box should only accept numbers
• Save file /home/user/MyDocs/one_up_count would be better as something like /home/user/.one_up_count so that it isn't visible to the user
• The fullscreen flash is distracting - I realise that's because you're using a standard button widget so this may not be easy to fix
• It would be nice to have an About menu option
• Have setting whether to save on exit: Yes, No, or Prompt (as current)
• Setting to make a little sound (different for add/subtract), so can use confidently without looking at screen
• Setting to not blank screen while app is in the foreground (the same way that media players don't blank the screen), or make the app work if screen blanked (not sure if the latter is possible), so that if the user is counting things that happen less frequently than their screen timeout, they don't have to keep unlocking the screen
• Ctrl+V to paste (i.e. like Set value but working directly on main screen). Maybe Ctrl+X to copy to clipboard and reset to zero at the same time
• Handle large numbers better, maybe by reducing the font size, or wrapping to a second line
• Font/colour options
• Orientation settings of Landscape, Portrait, and Auto, to allow the user to stick the orientation in, for example, portrait, which helps them use it without looking at the screen so they know that one direction on the rocker will always increment the number whichever way they hold the device
• Keyboard Controls menu item shouldn't have capital C. The help text itself could be displayed a little better

Hope this helps.