I've also been thinking about that notification of PM's that we were talking about speed when not displaying the user block and just using the tabs. If you have the login boxes, and after you have logged in it says welcome back 'whoever' it could then have dynamic links next to the welcome back bit. for example

Welcome back Fredski (logout) - 0 New Messages - New Posts

the new posts bit is for forum posts since last visit.

I'm sure that wouldnt be to hard to do