I've seen a few of these types of shows in Las Vegas: Le Reve, Zumanity and now KA. I have not seen the other Cirque shows so I cannot compare this to those, but KA on its own is a sheer spectacle. Amazing sets, performers and a giant rotating wall that serves as the back "drop" for most of the scenes. The performers in this show are clearly not afraid of heights, falling or death (some stunts are done without a wire).
I would totally recommend this to a friend and I would see it again if I could get discounted tickets. We purchased our tickets through Travelzoo for 50% off the regular price and we got seats at about the middle-left of the seating sections which was near enough to see the actor's faces but far enough to see more of the action that wasn't necessarily on-stage.