Moving to a buckling-spring keyboard (similar action as the Model M) relieved a great deal of forearm pain for me. I am naturally a furious typist, and the increased resistance seems to help.
I wonder if this is related -- it seems that people who wear shoes with less padding (or no shoes) are less likely to get certain types of injuries. With no padding, we strike the ground carefully. Wearing cushioned shoes, we strike the ground with full force.
I use a Unicomp too. I actually don't think they increase resistance, they increase actuation and positive response. That is what reduces RSI in this case.