My 20-40mm just came in the mail today. It was a combination Birthday/Christmas gift I bought for myself. It was selling Used in Mint condition for $574 at B&H. This beats all the prices for that lens I have seen so far.
Since it was dark when the UPS guy showed up, I didn't have time to test it in bright sunlight, but preliminary result from indoor photos I have taken, is that this lens beats all other lenses I have purchased so far, (although I only have 4 other lenses). The picture quality is just outstanding and very sharp and contrasty. Also it is a very quiet lens without the bulky SDM. There are no color bleeds like my 35mm f2.8 macro, even at high ISO settings and the Pentax colors and 3D-look almost matches my 77mm f1.8 !
I can wait till tomorrow so I can take it out and see what it really can do. Maybe I'll post some photos. Who knows maybe I'll be disappointed...
Compared to my 100mm f2.8 Macro which I purchased a few months back, the colors are truer, the sharpness and contrast are better, this all I can say so far...