The patched firmware, , has been something of a work in progress for a number of weeks, as detailed in . Lu that the custom firmware has been tested extensively by a number of individuals during the development period, and that the script is now in a stable condition, minus a couple of bugs. The two bugs currently found in the firmware include a problem with sound quality and active contents not working.
The will open up older Kindle models, such as the Kindle 2 and Kindle DX, to new features such as improved PDF support and better Web browsing. According to Lu, these additional features don't noticeably negatively impact performance on the older hardware.
You'll need to do a fair amount of tinkering to get the custom firmware working--including jailbreaking your device. You'll also need to Kindles--one old and one new. Why, you ask? Lu's script works by taking the firmware from the old Kindle, copying it over to the new Kindle, patching it, and then sending it back with new features ready to go. Got it?
And as Lu says in the "readme" FAQ:
"Why can't you just release the update package for my Kindle since all updates generated for one Kindle works for all others of that model?