It is already known that you can choose whenever start your session using Unity or the 'good old' Gnome Desktop.

This is possible ( at least in the 11.04 Alpha 1 ) by selecting the Gnome Desktop in the session dropdown on the login screen.

(In case your system has not graphic acceleration enabled ( i.e. compiz ) then the default session will be the old Gnome one.)

Also it is possible to remove the global menu behavior by removing the package indicator-appmenu ( there is not graphical settings up to now )

Also they assert that Unity launcher won't be moveable. ( http://www.omgubuntu.co.uk/2010/12/ubuntu-unity-launcher-wont-be-moveable/ )

versions 11.04 - 13.10

As the picture shows - "test" is a root menu which has been added.

To do this will require a couple of folders to be created:

mkdir -p ~/.config/menus
mkdir -p ~/.local/share/applications

Next copy the standard menu template file into the local menus folder

cp /etc/xdg/xdg-xubuntu/menus/* ~/.config/menus

Note - the stock XFCE menu could also be used - I prefer this menu so I've used it in my example:

cp /etc/xdg/menus/* ~/.config/menus

Now create our test menu - its in .desktop file-format

leafpad ~/.local/share/applications/test.desktop

copy and paste the following:

[Desktop Entry]
Version=1.0
Type=Application
Name=test
Comment=
Icon=acroread
Exec=acroread
Path=
Terminal=false
StartupNotify=false
Categories=X-Xfce-Toplevel;

The important bit is the last line - it must have X-Xfce-Toplevel as a category

Edit our custom menu:

leafpad ~/.config/menus/xfce-applications.menu

Add a new entry as shown:

Finally - lets use the custom menu file:

Right click Start and choose properties:

Choose the custom menu option and navigate and select the custom menu file ~/.config/menus/xfce-applications.menu