Some updates from me, after a few days of playing:
1) I logged a Feedback that Siri can't access my health data (UK region)
2) If you're having WiFi dropouts, try turning the new "Connectivity Assist" option off. It may help.
3) Weather app on MacOS can't be configured to show temperature/conditions as default. FB logged.
4) Dragging an app icon to a home-screen won't allow duplicates. All other instances are silently deleted. Workaround is to drag icons from the App Library. Bug existed in iOS 26 too. FB logged (again)
5) Screenshots can't be cropped at the point of saving. Mentioned loads of times above.
6) I have a shortcut which reads out my steps (that works, unlike 1 above). If I've walked a low number which looks like a year, Siri reads it out as such! "You walked nineteen eighty seven steps today". Duh. FB logged.
7) My iPhone 17 doesn't have much data on it, and it's still saying it's indexing. Whatever it's doing, it's doing extremely slowly. However, it doesn't appear to affect anything, as I got the new Siri AI yesterday (UK region, Switzerland location).
8) I love the new shortcuts method of combining shortcuts and automations (automations show as a trigger on top of the shortcut, but running it manually just skips the trigger). Shortcuts has been the thing I've played with the most.