These are going to be LEO satellites (no higher than a few hundred km), instead of GEO satellites, which would make the lower bound of the latency pretty low (comparable to cable or DSL).
Cool! Quick back-of-the-napkin indicates that the RTT for LEO satellites (at the upper bound) would be only ~4.7% of the RTT for GEO satellites. I'm sure there's much more to the story that I'm missing, but an LEO satellite should have a latency of around 11.75ms. In 2012, average US latency to Google was ~50-60ms [1]. Would bandwidth be the limiting factor?
http://upload.wikimedia.org/wikipedia/commons/8/82/Orbitalal...