This piece of hardware was pretty unknown for me until the purchase of my Amiga 4000T, But after been able to read some about it and also test it a few times I must say that it is a really cool piece of hardware.
Sadly, it is discontinued so it can not be purchased at the moment.
What does it do?
It makes it possible to change KickStart ROM from within Workbench but not only that, it does also make it possible to add ROM Upgrades from Amiga OS 3.9 Boing Bag’s. By doing that you can skip the reboot after patching the KickStart ROM at boot-up.
If that wasn’t enough, you can also load several modules in it. Example of that is SpeedGary which speeds up the RAM access, KingCON and many other things.
From firmware version 1.6 you are also able to re-kick back to KickStart ROM 1.3 🙂
If you find a KickFlash OS4 for sale and own a Amiga 3/4000, buy it (if it is working and price is not that high)!