Originally posted by RobG I'm wondering if there's a better lens in the 16-45 range
Yes, there are better lenses, but better in what way? What do you need that the 16-45 isn't giving you? WR? Silent focusing? Greater zoom range? More resolution? Better microcontrast? Better color rendition? Faster aperture.
I have a copy of the DA 16-45. I bought it instead of the DA 16-50 largely because of the SDM issue (I otherwise considered the DA 16-50 better optically based on images I had seen from both lenses). Although the 16-45 is a very nice, capable lens, with some of the best corner to corner sharpness I've ever run across in a zoom lens (particularly at the wide end), I found it wasn't keeping up with my other glass. The images I was getting from it didn't have quite the same vividness and brightness of color as my other lenses. It was most noticeable in prints, which just didn't have the same visual impact. So I purchased the FA 20-35 as an upgrade.
There are many other lens that, like the FA 20-35, are better, at least in some ways, than the 16-45. For WR, there's not only the 16-50, but the new DA 20-40 and the DA 18-135. Both Sigma and Tamron, along with Pentax, offer faster, f2.8 standard zooms. Pentax offers four standard zooms with focus moters: the DA 18-135, the DA 17-70, the DA 20-40, and the DA*16-50. While none of these alternatives are likely to offer significant more resolution (the DA 16-45 is pretty good in that respect), some of them (at least the Pentax star and limited options) will likely give you images that have bit more contrast and "pop."