GNOME 3 activities tab is always accessible by hovering the upper left corner. If you go into full screen mode with a java app such as netbeans (firefox works too - i believe since it is a "foreign" toolkit) you'll find that the window is still "rounded" even if you have no decorations anymore, which is quite nice because you can access the activities tab with the mouse and not have to go out of fullscreen or alt+tab to another app.
This doesn't happen with native applications put into fullscreen (such as gnome terminal). Those are always square in fullscreen. Unfortunatly it doesn't appear to work if you never were decorated (my app, when deserializing). Nevertheless, this is the first time i encounter a UI bug that actually enhances usability.
