Empiricism trumps theory. You theorize people don't type fast enough for it to matter, but a large number of programmers, including me, report that ergonomic keyboards help them. Why are you arguing against the evidence?
I've tried ergonomic keyboards and was turned off by the lack of key feedback. I never really got to whether the shape was better or not, just that the mushy tactile key press experience was vastly inferior to my Model M.