Remove "The Software on this Computer is up to date" message
This is just a small annoyance and might be subject to taste.
After an automatic update Update Manager displays the message "The Software on this Computer is up to date". This message is unnecessary and distracting and was not present in Ubuntu 12.04. It is an elementary part of user interface design not to display messages when a program runs as expected. When I confirm an automatic update, I expect that update to finish. Thus I only need messages when an update failed.
Since update take some time this message might interrupt my work flow at unexpected times for not reason. I do not know why it was introducest but it should be removed if there is no compelling reason.
Here is an image of the dedicated window displaying the message: http://