Comments about Pentax SMCP-DA 17-70mm F/4 AL SDM Autofocus Lens for Digital SLR:

This modest aperture zoom lens gets my heaviest use indoors and on location. Mounted on a high-ISO-capable Pentax KX, the F4 aperture is not a drawback in low light. Sharp at 17 through 70mm. Use it with confidence at F4. Stopping down gives marginally improved sharpness.

Another plus is the distortion and chromatic aberration reduction engineered in the Pentax DA lenses communicating with the Pentax bodies. These in-camera corrections have saved me a lot of time in postprocessing. It is another reason I have not sought third-party lenses for the Pentax bodies.

Could it be built even stronger? Yes, but additional weight could be a drawback. If you own a Pentax body and desire more focal-length range and IQ than the very good 18-55mm kit lens, you shouldn't be disappointed.