Ka was amazing. It was my first cirque show (although I'd see them on TV) and completely different than I expected. The theater is great - there are really no bad seats in the house. The production design is incredible! The show has a story which is quite convoluted and tough to understand, but if you just go for the show, the amazing acrobatics and the beautiful sets, you will not be disappointed.
As mentioned, the tickets are quite pricey, but if you're able to get the BOGO for $25 or the 1/2 price tickets (which I was able to find) it's totally worth it.