Rotary encoders are awesome because they function like knobs – a staple of user interface which needs no explanation – but electrically they generate discrete button presses, like pushing the Up or Down tuning button. They are reduced to mostly awesome by some designers who apparently don’t know how to use them correctly.
Case in point: the Kenwood VR405 surround receiver I recently picked up from the side of the road.
It’s a cheap and basic surround reciever, but it works (other than missing the volume knob), it was free, and it has a cool-looking rotary encoder on the front panel. Rotary encoders are like the bling of tactile input devices. Buttons are nice and all, but things that spin are just so much cooler. They also happen to work really well for linear controls like volume and tuning, for which they have been used for decades and still should be more than they are. (I’m looking at you, designers of 1980-s electronics-with-no-knobs and of infernal-car-stereos-with-button-densities-approaching-infinity.)
However, Kenwood got it completely wrong on this model: the input selector is rotary and the tuning/everything else “Multi Control” buttons are Up/Down buttons. Unlike rotary selector switches of yore this input selector wheel has no detent to tell your finger it has reached the next setting. This makes changing inputs quickly is very easy but stopping on the right one is very difficult. And tuning? Click, click, click, click, click, as fast as your finger can push the button you can change to the next frequency. Tiring. Why on earth didn’t they use the up/down buttons for the input selection and the rotary for tuning, like, you know, old-school tuners used to be? Some of the pricier models in the V/VR series were slightly better because they had a rotary encoder for both the Input and Multi controls, but Kenwood could have saved a couple pennies and given users a less frustrating UI at the same time by just using rotary for the Multi Control and buttons for the Input Selector across the whole line.