I really liked them on my commuter bike. The first time I used them I noticed a consistent increase of my average speed of about 2km/h (over regular Schwalbe Marathons).

That being said I did swap out the rear for a regular marathon after I wore out the sidewalls prematurely. They are fine on tandems but on an upright Dutch commuter bike I sometimes carry people + bags on my rear rack which easily brings the load to 180kg (360 lbs) over a single wheel which they simply weren't designed for.

The only thing that would make them better was if Schwalbe made then with brown sidewalls for that classic look.