I distinctly remember using CDE back in 2005 on a Sun Ray 2 Thin Terminals. It was serviceable however I must confess I had a hard time getting used to it, especially after using Gnome 2 and KDE 3.

The one great thing about them was that you could use a chip and pin style card. If you used this card when logging in it would associate your session with the chip and pin card and when you logged into another client (by using the card) your exisiting session was moved across. Which I thought was pretty novel at the time.

When I have time I might give this a try out (for nothing other than nostalgia reasons).