Absolutely, positively do not buy this hub for use on a bike with anything other than horizontal dropouts. Sturmey-Archer no longer makes anti-rotation lock washers for vertical or other dropouts, and the hub absolutely will not function properly without them. I have had extensive contact with Sunrace (the manufacturer) and their US parts distributor and the hub is nothing more than a complicated paperweight without the proper lock washers. I machined custom lock washers and still have not gotten the hub to stay in gear (any gear!) without slipping under normal pedaling load, even after painstaking cable tension adjustment. What I've heard from a bike builder with extensive experience with internally geared hubs leads me to believe that this hub might not work at all, even with horizontal dropouts.
The S80 series of Sturmey-Archer hubs are one of the best values in the hub market today. Though the company lost some of its mojo in years past, they have a very strong lineup and the quality seems to be excellent. The hub was built up along with a polished CR-18 rim and the combination is gorgeous! The hub spins more freely than the Shimano hub that is on my wife's bicycle and the built in drum brake makes for strong braking when it is needed.