Well, I can't speak for the Redledge stuff, but I am a HH hammock user with an exped. I recently spent a week on the trail in the Wind River range, and because I wasn't certain I'd always be in ideal hanging situations, I took the exped along. I indeed spent 2 days on the ground, and was exceedingly happy to have the exped. You give up a lot of weight over the SS system, but gain the ability to go to ground.
My hammock set-up uses a JRB quilt set as well, so I was only using the exped for situations where I went to ground, or partially inflated in temps below 50 or so.
I think if you check out the forums over at http://www.hammockforums.net you'll find extensive discussions on the practical use of the SS system. Reviews seem to be mixed. A lot of folks over there use the exped as either a go-to-ground option, or as their primary bottom insulation.