"I've sheared off a shaft & prop twice in the last ten years "
For you definetly, ever consider a navigation course?
)just kidding MM!!
I've dinged a few props but never cleaned it off completely (came close in moriches though). For most others wiping out the bottom is a pretty rare event .
Also, if you shear off the entire thing, it may not be destroyed. It is designed to shear off. cost of shear pin is about $1.00
(just kidding) If you wipe off an inboards hardware, there usually is some damage to the hull, it is not designed to break free in event of an impact.
Most people that really wipe off shafts and struts normally end up on a reef (a la that large Sport Fisherman on Pigs) on the beach or sink altogether. This system, you actaully don't do hull damage if you wipe it off, the boat is intact. There may be an insurance rebate....lives are more $ then outdrives
Although exposure is an issue and I would not use a drive like this fishing tight to the beach, for a lot of boaters this is a good solution. (the sea-ray weekender types) There is no doubt about it in my mind, there are a lot more +'s then -'s with this system.: