Even though I don't like the "air" mattresses, I will say that I agree that Comfortaire is going to give you much better customer service (and on the queen size and above) there is no foam piece down the middle. If you decide to return the bed, Comfortaire is definitely "no questions asked, no hassle." Not the same with Select Comfort. Remember, with Select Comfort, you WILL be paying for the advertising and the store in the mall.
In my area, there is only one mattress store (about 45 minutes away) that carries Comfortaire. Otherwise, you can order it off the internet from a mattress seller. I think when I ordered mine, the Select Comfort bed was running about $1700, and the Comfortaire "twin" was about $1000.