I have both an A2 and an A3 Asymmetrical for my 43DS. They are very efficient and better for tight reaching than a symmetrical. I compete in the Port Huron to Mackinac race as well as other buoy races during the year with them too. When the wife and I are on out boat sailing by ourselves, I add the sock and it makes all the difference in the world in sail handling the two of us.
We had a Quantum A2 on a custom sprit for our last boat, and it was an excellent addition to the inventory. After we got it, the symmetric spinnaker and pole came off the boat. It is just sooo much easier to use the A-kite.
We are just in the process of finalizing our asym setup for the new boat. We are looking at about cdn$4k for the kite, $3k for a top down furler, and $1.5k for a Selden bowsprit. It's a lot of money, but definitely a worthwhile upgrade!