There are some window managers that our unity mode does not work with: viewport-based WMs (Compiz, Enlightenment) and Ubuntu's unity. If the guest's WM is one of those, our unity mode is disabled.
Fair enough. I had a Unity 2D configuration working with VMware Unity in Oneiric but I've since lost that VM. Vanilla Ubuntu 11.10 and 12.04 uses metacity as the window manager and I've tried several combinations of Unity 2D with various managers, none of which enable VMware's Unity mode properly.
I'll keep experimenting until I find a working a combination. Input from others welcome.
Thanks for your help