As with most things outdrive design has improved over the years. Most of the disadvantages listed relate to old technology. Volvo has been the leader in this area. Their outdrive legs are made of composite, so no more corrosion problems. The have also been designed to raise higher for better clearance. The synthetic gasket material today is very reliable. I have built over 100 yachts with saildrives with similar sealing gaskets and never had a problem, this is with yachts in service for over 10 years. Additionally Volvo offers Duoprop technology which can improve fuel economy by another 20%. I do believe the drive train is the most susceptible part of an inboard install. Stuffing box, cutlass bearing, coupler, keyway, alignment etc. That is why I am currently a big advocate of enclosed shaft systems with inboard installations. Though it costs more, I for one would not do another inboard install any other way.