Didn't go quite so well.

[bucker00]

Thought I would post this here - my upgrade didn't go quite right at all.
The first update to _4 went fine.
I normally have 4 gateways showing (2 IP4, 2 IP6).  After the second upgrade to 25.1 three of them were missing and no internet at all.
The UI showed 25.1 as the version but with the old logo and 4 new temperature sensors had appeared with 100 degree readings.
Reverted to pre-upgrade ZFS snapshot and tried again with the same result.
I've gone back to that snapshot again and will clean install tonight after work.  Sorry I didn't get logs but can do another test if required.

[bucker00]

Did a clean install then restored a backup. 
Below is a screenshot of the not-great upgrade dashboard in all its glory.
My temperature sensors still look like this though although the logo and network problems are resolved.
A screenshot of just the temperature dashboard widget after the reinstall attached also.