I love my Apple Watch. I use a Series 3 and I can not understand why I would want to upgrade it as yet. While the digital crown is more annoyance than evocative of the crown on a wind-up watch, I would not buy a new one to avoid it.
The Apple Watch 'digital crown' is a knob that spins. You could wind a digital camera between exposures, but that'd be stupid. Using the crown as screen navigation input is OK but I am willing to believe they can do better.
So, that's pretty clear. Instead of the Digital Crown, the patent suggests an optical sensor in its place.
A direct replacement, then, because the abstract goes on:
"The input component provides a user experience that simulates user interactions with a crown that is rotatable and/or translatable."
I'll be honest, I'm not sure about this change and my hesitation is this: the Digital Crown is part of the essence of the Apple Watch. It is a delightful evocation of the winder found on a traditional watch, it sits in just the right place and works perfectly. Of course, the current version is very different from how it was on the first Apple Watch.
Winding a watch is a tactile pleasure, much like winding a Rolleiflex camera loaded with 120 roll film. It is annoying, however, when my watch stops and I need to set it and wind it every day. Again, we do not wind our digital cameras.