It sounds quaint, but one of the most common tasks I use my Apple Watch for is to set timers. I have timers for everyday things around the house (coffee, laundry, cooking, etc.), and it's also wonderfully helpful when you just need to time something randomly throughout your day. Seriously, I use this feature all the time. That is why I'm so upset by the change to UI that the app has taken in watchOS 3.
Apple is trying to add simplicity, but doesn't quite stick the landing. In watchOS 1 & 2, you could launch the Timer app and spin the Digital Crown to get to the time you wanted to set. Now in watchOS 3, Apple has tried to make things quicker by giving you 10 common durations that you ca activate in a single tap. If you have a timer that doesn't match one of the 10 presets, then you can scroll to the bottom and tap the Custom button to bring up the old interface and set whatever timer your want.
This is good in theory, but in my case is a disaster in usability. This app that used to let me set a timer incredibly fast has been slowed down considerably. Apple may have the data to show that the times listed in the above screenshot are the ones I'm most likely to use, but I never find myself using any of these.
I use a 4 minute timer for my coffee, a 46 minute and 75 minute timer for my laundry, and a whole mess of different times for cooking. But what remains constant is none of them line up well with the presets that Apple has provided. This means that every interaction with the Timer app is now lengthened because I need to scroll to the bottom of the app to select the Custom timer option and enter it there.
I don't think that Apple's design for the app is completely wrong, I just think they need to modify it a bit. First, I'd move the Custom timer option to the top. Even if there are common timers you set, I would wager that most people want to set a custom one most of the time. I could be wrong, but if I'm not, this would make most people's default interaction a little easier.
Next, I'd allow users to customize what their pre-set timers are. The idea of default timers is a good idea, but they should be less generic that what Apple is currently offering. By letting users set their own timers, they could ensure that this feature is as useful as possible for the most people.
P.S. Yes, I have filed a radar for this as well.