we've discussed the concave bottom of the Heiny-can causing turbulance in the flame on some burners. i fixed it! i'll post pics in the pimp thread in a day or so.
I believe that turbulance can be benificial to efficiency as it slows down the flame over the bottom of the pot therefore allowing better heat transfere to the water. I have a scientific paper on the topic and I have been trying to design this feature into my stoves.