Martec Performance
I agree with the assessment that both sailing speed and pointing were improved with no loss in motoring or manouvering under power. I installed a Martec when my 28.5 was delivered in 1986. The only negative we've experienced is a difficulty to 'open' the prop with significant forward momentum. Opening the prop if your speed is 3-4 knots takes a good burst of throttle; which, if only one blade opens, can cause some shaking until the prop is fully open. It may be prudent to 'heave to' or do a 360 for an 'emergency' stop under sail. Our normal proceedure in dropping sails even when single handing, is to start the engine, put it in forward at idle, come head to wind, and drop the genoa. At that point we've lost enough forward momentum that the prop is already open as I increase RPM's and go forward to drop and flake the main without blowing off course with the wheel 'locked'. For larger or heavier boats, or full keeled boats with the prop in an aperature, I'd assume a geared feathering prop would give the sailing performance of the folding prop with better reverse operation (but possibly higher cost). Another plus for a folding prop in Chesapeake Bay, is that you are much less likely to hang up on a crab pot under sail; which makes night sailing with pots around less of a concern.
