I don't know about formats settling down, polen. Have you used Calibre to convert from one format to another? If you still like your current reader you can always convert epubs (for instance) to mobipocket, as long as there's no DRM issue.
If you decide to buy new, there are lots of good choices out there (in here??) depending on what you want most -- library access, clear-looking screen, buying from your device . . .
