I have reverse cycle a/c in my AORC cross-over camper. In the 41 nights I have spend in my van this year, I have used it on 1 trip - though I guess the weather has a big influence on this. It has two issues, 1) its not the quietest thing around and 2) it needs 240V power. I also have a 12v fan (Siroco) and this gets used FAR more. I see the KK is a 12V a/c but with around the same cooling capacity as my 240V unit. Thats going to need some battery power and I cannot see how it can run for more than an hour or so - just do the math on power consumption.
I also have a diesel heater and that gets used regularly. Recently a friend ordered a camper the same as mine and I recommended he only get the diesel heater and Siroco fan and forget the a/c. Its "only" a $2,500 option and still not value for money, $10K is simply too much IMHO.
Cheers
Captain