It would be helpful to have the user name included in the "Sign Out" mouse over text.
The reason is we allow Guest access to certain graphs. This allows us to email graphs and have them open without having to sign in.
The UX issue is that it's not clear whether you are logged on as Guest or your normal account.
A user came to me yesterday and told me they couldn't see Maintenance windows. I told them they weren't logged in. They showed me the "Sign Out" mouse over.
It was a bit confusing that they were logged in as Guest, so had to sign out and sign in again as themselves.