I'm a fan of Plastic. From the GUI to the feature sets, I think it's near perfect.
However, I'm disappointed at the recent GUI changes to the Plastic SCM client. The quick-switch workspace tabs are now replaced with a drop down menu (top left corner).
For a studio that have multiple projects running concurrently, this takes one more click to switch workspaces. Not a big deal at a glance...until you find yourself having to switch back and forth often as the project manager.
Please consider bringing back the tabs. I don't see a reason for changing the GUI for this just to sacrifice fewer clicks for a few more pixels of screen estate.