I just built a two stage dust collector using the Thien separator. I used a 2hp HF dust collector and a Wynn .5 micron filter. The strongest thing I can say is 'incredible'. I have a table saw, band saw, and planer that have 4" dust ports. I built the dust collector on wheels with a 10' hose. I just move it where I need it, hook up the hose and go to work.
The Thien separator is built under the lid of a 30 gallon galvanized garbage can. I have only a 1/4" foam weather seal strip attached under the lid, but no leakage. I have emptied the garbage can twice and still have no sawdust in the clear poly bag under the Wynn filter.
More importantly, no fine dust layer on anything in the shop.