@Sphyloid Whilst I accept what you say may be true as a general statement, it only applies to situations where motor torque is a limiting factor, and with the light weight tool heads that 3D printers use, achieving the desired torque is easily done by selecting an appropriate motor. For 3D printers the overal print speed is limited by how fast you can melt and extrude filament, not by how fast you can move the hot end in X or Y directions. So I have to disagree that any form of fancy acceleration control is going to reduce print time at all, let alone cut it in half.
Whilst I accept that there may be some benefit in using S curve acceleration with CNC tool heads that have mechanical cutters, I fail to see how one could coax the filament being forced through a tiny hole to faithfully follow an S curve acceleration profile in the same way that the hot end carriage might. Smooth linear acceleration of molten filament is difficult enough to achieve, due to the severe damping effects and time lags involved with melting filament and forcing that viscous fluid through a tiny hole.
