All,
I wanted to say thanks for the great discussion and ideas on this board. After suffing for many years with a perpetually clogged shopvac filter I cannot say how impressed I am with the effectiveness of the Thien seperator. I did a little write-up on my blog. It may be bad form to reference you there instead of re-typing everything : but I am going to do it anyway! :)
http://widgetninja.wordpress.com/2012/05/01/dust-seperator-for-the-cnc/
I cannot think of anything i would change or do different in the design. My only add is to make a dolly of some sort to put the bucket/shopvac on the same platform for easier mobility.
-Rob