In a recent podcast Paul, Erica, and Ernie were recounting their latest experiences in competitive water boiling, pitting a rocket stove against a gas burner. At one point the possibility of reducing the heat that is dissipated around the sides of the pot was discussed, and the idea of came up of surrounding the pot with something that would keep the hot air in contact with it longer.
An alternative way to increase the efficiency of the heat transmission from stove to pot might be the "Cajun Rocket Pot" http://cajunrocketpot.com/. I remember hearing it advertised on the radio a couple of years ago. It's basically a normal pot with a bunch of metal dowels welded to the bottom to increase the surface area of the bottom of the pot. So it's kind of like a reverse radiator, increasing the transfer of heat into the pot, instead of dispersing it as a radiator is normally used.
It wouldn't really tip the scales on the rocket stove/gas burner competition, but it seems like it could be another trick to wresting additional efficiency from a rocket stove.