A PW3 running 5.8.11?
Serial port only.
No performance change.
Our "jail break" is only a signature certificate added to the key store so people can install our packages.
KOreader is one generally useful add-in
You will already have a serial port install, short of frying the silicon, with serial port access you can fix anything.
The jail break is "viral" - it auto re-installs itself after an Amazon update.
(except for the KOA2, where it is currently rather broken.
)
All answered in the first post of this thread.