... 'About Firefox' menu option now automatically opens a 'release update channel' and automatically installs the current version (if more recent that the one currently installed on my PC).
I personally find that merging of 'About...' and 'Update' into one was a very sensible move and would like to suggest that you also consider it in future....
I can't agree with that. It's better to have option wheather to update. For instance if a user is going to abandon the existent snapshot soon, than this forced update is only a nuisance.