Pentax DA 40mm f/2.8 Ultra Compact Lens

Pros: Tiny and extremely well made.
Pin sharp with good contrast, even at maximum aperture.
Image bright in view finder.
No detectable lens aberrations.
The unusual aluminium lens hood is well designed, and it does its job well.

Cons: Nothing negative at all from my point of view.
Some might not like the tiny screw in lens hood, or the fact that the lens looks weird on a dSLR. But in my view these are not defects

Summary: I bought this lens from Amazon as a fixed focal length prime lens for my Pentax K20D, and it has far exceeded my expectations.
It is tiny and extremely well made. So far results have been pin sharp with good contrast, even at maximum aperture, and the lens displays no detectable aberrations. With a 35mm equivalent focal length of 60mm it's fair to say it will make a decent portrait lens too.
The aluminium lens hood is unusual but well designed, and it does just as it should.
All in all this is a first class prime lens and a steal at the price. Anyone with a Pentax K type dSLR should have one of these.