Issues With the UI
Granted, this issue is completely subjective, but a lot of users are complaining about it.
As it turns out, Apple decided to change the location of a lot of features in watchOS 10. For instance, pressing the Side button now opens the Control Center, whereas before, it gave you access to your Dock.
People are also complaining that you can’t switch watch faces by swiping to the left or right anymore and that the Grid view on the Home Screen is also different.
As we said, take this one with a grain of salt. If you don’t mind these types of changes, you won’t be bothered at all. It just takes some time to get used to.