This is just a PSA which I'm sure most of you know, but I thought I would pass along. I have the original 42mm Apple Watch, and with watchOS 4, I noticed performance became really bad to the point where I could barely do anything on it. The most egregious thing was trying to set a workout - for whatever reason, when I would go to that screen, it would remain frozen and I would be unable to select a workout. On a whim, I restored my apple watch and set up as new, and surprisingly, it works a lot better now. The workouts app works as expected, and everything is a lot more fluid. In the past I have updated but restored my settings from the backup, but this time setting up as new really seemed to have helped. Hope this helps someone!