Great writeup by Marco Arment on how he completely redesigned the Overcast watch app after actually using it:
Trying to match the structure of the iOS app was a mistake. For
most types of apps, the Apple Watch today is best thought of not
as a platform to port your app to, but a simple remote control or
viewport into your iPhone app.
My initial app was easier to conceptualize and learn, and it
closely matched the iOS app. But it just wasn’t very good in
practice, and wasn’t usually better than taking out my phone.
The new app is a bit weird and polarizing, and has a learning
curve, but it’s great in practice if it fits your preferences.
(Just like the Apple Watch.)
The original design wasn’t bad at all — it was actually one of my favorite third-party Watch apps. But the new design is clearly better.
I think every developer who started working on their Apple Watch apps before actually owning an Apple Watch would do well to reconsider their designs. It’s one thing to know you shouldn’t simply design like the Watch is a small iPhone. It’s another thing to have a sense of what makes for a good Watch app — and you have to actually use an Apple Watch to gain that sense.