I bought a Forerunner 255S earlier this summer. I don't really care too much about the speed logging accuracy (I'm slow), but I like being able to log my activities, including the gear I used and add notes and photos to each session. I'm also taking a snapshot of our club weather station graph when I end the session. It kind of reminds me of the days when I used to log all my windsurfing on MyTrims.com.
I made my profile public, so if you want to take a look, feel free to do so:
connect.garmin.com/modern/profile/e5b7cdb7-c3b8-4340-9294-f52407aa9722It's nothing special though...I'm not all that great at wingfoiling even though I get a lot of time on the water. I don't always write an extensive note, but I will grade each session using an A to F grade system (with +/- for minor adjustments).
As far as the UI on the watch, I just configured a custom activity for winging (and windsurfing), but I don't get data like 5x10 etc or even last run maximum speeds etc. For me, it's enough to get a session max, average speed moving, time and distance (and heart rate is nice too).