Here's a patch against Enlightenment 0.16.7.1 that adds better transparency support under the CVS version of X.org. It's a little rough, but th patch basically makes windows partially transparent during an opaque move (real transparency, not the faked nonsense built-in to E16), and it adds a "Transparency" menu to the window operations menu (eg, the menu you get in most themes when you right-click on the title bar, or when you ALT+right-click anywhere in the window). You'll need to clear your cached version of menus.cfg in order for the new menu to show up. Here's a screenshot:
For those of you who haven't seen X.org transparency in action yet, here's the first screenshot I took once I got it set up:
Finally, if you're planning on setting up X.org, but don't know where to start, you might try reading my setup notes.