I've owned 2 of them, and still have my original.
They are great sounding amps. I love the built in noise gate.
I wish every amp would have one, and a reason why I am looking forward to the upcoming Armageddon's with their built in ISP soon.
I found the regular JCM800 side a bit twangy, and the Beast side a bit compressed with too much gain. But I run most amps with less gain, so I would always run the preamp around 1-2oclock, and then the assault (beast) around 9am. This gives a very tight and heavy tone. higher than that is crazy gain. Very deep and thick amp with lots of volume and punch.
I first tested it against my Mesa Stiletto II Deuce, in the shop, and thought the Stiletto would wipe the floor with the KK....but I was wrong. Very wrong, and got rid of the Stiletto very shortly afterwards.
They are good amps, IF you don't need much.
When I play that amp, my path is Guitar, cord, amp. nothing else.
I was playing the KK at THIS show...