You're probably the only person that liked the X11 version. I've been a longtime SlickEdit user, but that X11 garbage on Mac was so horrible that I just used the Windows version in a VM or TextMate. Presumably you can install two versions in different locations and keep using the old one if you like that junk. There's no real feature differences, just the UI became useable. I guess it was usable in X11 if you didn't mind screwed up key bindings and never needed to copy/paste between VSE and a native Mac app.