I have great respect for the original designer, who really wanted to build a bike with as few parts as possible. He felt that bikes with derailleurs and gears were just too complex, and that his ideas solved those problems. I have two of these bikes, and they are very well built with good quality frames and parts. The narrow 24” wheels roll fast and make pedaling easy. The wheels are alloy, the frames are lugged, and the rear only brake is powerful.
These bikes were intended for Florida retirees who just wanted to get out for an occasional ride. The gearing range is not wide enough - not low enough for big hills, not high enough for real speed. The gear changing operation makes sense, if you have not ridden a conventional bike in 20 years. The shifting action works well enough, but it’s not like any other bicycle. The rear brake is too strong and can be grabby compared to a normal canti brake.
I have one of the original Yankee bikes, and one of the later Nordic Track models after they bought Yankee out. This is a bike that can easily be sold on television, just like those AutoShift bikes and the ShaftDrive bikes. In practice, bicycle dealers didn’t want to sell them and they have a bunch of proprietary parts that bike shops did not carry.
If you’re a collector and find a nice one, buy it. It has a ton of good and different ideas , but it could not beat conventional bikes and was not capable enough for dedicated riders.