Don't really have an opinion either way but I wanted to remind some of the posters that they now have air beds that sit off the ground by a couple of feet. They don't just lie on the ground any more. In fact if you put sheets etc. on them it is hard to tell just from the height. But if the money is no object then I guess a Murphy makes more long term sense.
Similar to this:
http://www.airmattressesbeds.com/raised-aerobed.htm