As you quoted, I've never heard anything but praise about Century Optics products so bought the converter here in Prague without trying it. (they actually didn't have one in stock and had to order)
I'd destroyed the tests I talked about but have just done a real quickie so as to illustrate the degradation. Low and behold on this test there is no noticable loss of image quality. Perhaps I hadn't attached the converter properly in the initial testing, although it's a bayonet fitting...strange
Anyway heres a 2meg comparison pic with grabbed frames, stretched in Photoshop and resized to 1000 pixels wide http://www.electrickiss.com/WAcomparison.jpg