[8.9" Kindle Fire HD Android Development] Slimepuppy:
Just a couple of assorted comments from a relative newb that's exercised and broken this boot loader. ;)

KFHD 8.9 16GB

The end first:

- Backup your stock system files and move the files off the Kindle before installing TWRP

- Backup your configured system and move the files off the Kindle after installing TWRP

- Flashing boot.img, recovery.img, and system.img in fastboot will remove the TWRP bootloader and return the Kindle to stock

- It's just as quick and easy to install TWRP the second time around - yes, use the Freedom image 'again' if the device has been flashed back to stock (TWRP not present).

- Hashcode tells us to backup our systems and save the files. If we don't do that, rooted stock images are available from a number of developers, including Onemeila and Prokennexusa.

- The Onemeila and Prokennexusa tools include fastboot/ADB drivers, so there no need to install any SDKs if you don't already have and/or need them.

The story...

Hashcode's install process worked perfectly and I've enjoyed the freedom of moving back and forth between different versions of the Amazon software and his CM10 Alpha within minutes. The utility and the backup.restore process is a toaster - it just works!

During the process of learning, installing and deleting a bunch of software, and testing a couple of toolkit apps, I had remnant files, directories, and other strangeness that I wanted to completely purge and reset to 'stock.' Yes, that's the set-up. ;)

TWRP made it very easy to backup and restore, and it also makes it easy to do a complete wipe of the system, caches, user files, etc. etc. which I did. Unfortunately, what I "didn't did" is copy the backup files off the Kindle. And that created an interesting challenge, as I found myself with TWRP but an otherwise blank device. I wonder how I'll move system files onto the Kindle now?

I tried the TWRP sideload function, but couldn't get the Windows PC to recognize the Kindle while in TWRP - attempts to sideload failed. If anyone has a fix for this, I'm interested in learning it! Is this where one might use an OMAP driver?

I've successfully used Onemeila's restore images in the past, so brought those to bear to reflash the stock files in Fastboot. But the images for the 8.9 include only the system, not the boot or recovery images. Once that sunk into my newb brain (after staring at the orange kindlefire logo), I dug around until I remembered that Proconnexusa's tool included a three-image download in their restore process. If you use the Proconnexusa tool, let it run through downloading the image files (or pull the files manually) as the default process assumes the Kindle starts the restore process in ADB mode...

Pushing only the system.img leaves the Kindle in the orange kindlefire portion of the boot process - it sticks there and doesn't progress. I needed to also flash boot.img and recovery.img for the Kindle to move from the static to the 'animated' orange kindlefire portion of the boot process and ultimately into a functioning system.

Even after overwriting the TWRP boot process, the Kindle was never bricked - I always had access to the device via Fastboot.

Too many words, but I hope it's useful to others that install this excellent tool! Thanks Hashcode!