watchOS 8.7
According to Apple's release notes, there are no new prominent features in watchOS 8.7. Instead, the software focuses on under-the-hood "improvements," along with bug fixes and important security updates.
Fingers crossed, but this seems to fix the bug introduced in watchOS 8.5 where complications wouldn’t update.
Previously:
Update (2022-08-29): After using this for a while, I’ve found that the compliations situation is improved, but updates are still not as prompt and reliable as with watchOS 8.4. I’m also now seeing an intermittent problem where sometimes my watch runs out of battery halfway through the (otherwise unremarkable) day, whereas normally I end the day with at least 50% power remaining.