I saw Ka in Vegas a few years ago. It was amazing. It's martial arts based, so different from a lot of the Cirque shows. The theater it's in was made for the show so it's almost a prop in itself (you get puffs of hot/cold air directly at your seat depending on the scene). The stage tilts and rotates almost entirely vertically too, so cool.
Quidam is great. LOVELOVELOVED Iris. So unfortunate that it closed. As the Vegas shows go (aside from Mystère) "O" is tops on my list. Zarkana is stunningly beautiful to look at, and Zumanity is just plain fun. :-)
If I remember right, one of the biggies had a freestyle that she rode to Quidam... can't remember who though. Anky maybe?
The ninja monkeys are plotting my demise as we speak....
I am so lucky to live in a city that hosts these amazing shows, I lived in Cleveland for a year and never even went to a concert or anything. Now I am in Charleston with a bit more time and a bit more $, I am going to see as much as I can. As far as Mystere goes, I would love to see it, but the WC will have to come back to Vegas!!!
Always remember that "perfection" is the mortal enemy of "excellence."