I like this lens. Overall image is very sharp, especially at f/4.0-f/8.0. Colour and contrast is also good at this aperture range.
Wide open, image quality degrades slightly, but is not a major concern as I prefer to shoot with a bigger DOF for WA photos, meaning the lens will be stopped down for most shots.
One thing I particulary like about this lens is that distortion is well controlled. On full-frame shots (without digital crop factor), you get very good-looking perspective shots with very little curvature on the edges. On DSLR with 1.6x crop factor, distortion on edges is further minimised - not only that, the focal length converts to a comfortable 38.4mm which I think is perfect to use as a standard lens.
Overall build quality is fairly good. It has good sealing on the front to minimise any possibilities of dust getting inside - as well as being small and light for walk-around or travel photography. The only downside is the manual focus ring which is a bit flimsy for my liking. Overall, an excellent performer for its price. Paid 38,000 Yen for this lens brand new from a photographic retailer in Japan (roughly £195 GBP) - a very good Quality/Price ratio IMO. Am very satisfied with the results from this purchase.
(lens used with EOS 500 and D60)