It's a good lens design in terms of sharpness, which is all this test will care about.
I think most people thought (including me) that other lenses gave more pleasing pictures. Whether that had to do with color transmission, microcontrast, contrast or a combination of these, I don't know. In fact I thought the original DA 18-55mm gave better results in terms of the colors and rendering - but then the resolution apparently suffered, so they had to release the II version.
The same optical design was also released, with a significant tweak, as the HD DA 18-50mm retractable lens. The tweak is that the ELD element (extra-low dispersion) was substituted with an anomalous dispersion glass - the same kind of special glass used in the DFA*70-200mm. That was probably done so that Pentax could market the lens, as they
still do on their site, as a "high resolution lens for modern sensors" such as the 20MP and 24MP that had been recently released in the K-3, K-S1 and K-S2.
Note that the SMC version that came with the K-S2 as a kit lens states that it used an ED element - not the anomalous dispersion element. That would explain why the pictures I see with the HD version were always a bit better than the SMC pictures (HD coatings help there too but usually the difference isn't as significant, see HD vs SMC DA 55-300mm f/4-5.8, for example, the difference isn't big). The SMC DA 18-50 would be similar in quality to the older SMC DA 18-55 (II and WR Versions).
Long story short, I bought the HD DA 18-50 and could not be happier.