It has the same optics as the FA20/2.8, which I have. (The difference is the # of blades, 6 vs. 5). It's a great wide angle and fairly compact. Like Pentax's best lenses, it produces crisp images but renders them in rich, contrasty colors.
Lots of comments about the A/FA 20 lens here
Stan's Pentax Photography
The main criticism of the A/FA 20 lenses is that there is slight distortion. My response? To be brutally honest, if barrrel distortion is a "problem" then one is using the wrong tool for the job. If I photographed only architecture and graph paper I need to use a tilt/shift lens, not a rectilinear. In normal everyday application, like landscapes & street photography, distortion will not be an issue.