That info is pretty much spelt out in the technical support documentation on the Schealbe website.

Personal experience? I'm about 160lbs and have run those tires as low as 30 PSI when running on crushed gravel and limestone bike paths and expected to see some major drag issues on paved roads as a result. What surprised me was that there was probably a difference, but it was so negligable that I couldn't personally pick it out. I guess you'd have to measure it in a lab or over an extended distance, but IMO that kind of thing would only be omportant to someone doing competition.