I forgot to say you might have to go into preferences and go to keyboard and mouse, then choose keyboard shortcuts and make one...name it "Page Up" and then choose it...i chose apple+up and then your all set...it helps alot!
If you're used to clicking on the arrows and having to wait while the bar scrolls, just left-click on the scroll bar and drag it to the top. Nothing much faster then that.
I'm surprised there's no way to go directly to the first message, seems like pressing home who intuitively do this. I guess maybe in the update they will have this, without having to use the mouse.