Now that the public Beta of iOS27 has been out a while, I have pushed the 27 updates to my phone, watch and TV. So far the only noticeable update has been the removal of the WalkieTalkie App from the Watch. Not a massive loss, but was useful when running to call out live updates to fellow runners in the group if spread over a course, or when shopping with the family to coordinate when separated.
I have not yet noticed any improvements to Siri, but unclear if the backend has been switched over to Google yet and I don’t use it that often anyway.