The Tamron 17-50 f/2.8? I don't remember any of the specific articles (or threads I searched and found on here), but when I was researching, I did find quite a few. In the end, I ended up choosing the Sigma. I think the image quality (based on articles and reviews) is slightly better on the Sigma, but they're both good lenses. The Sigma also has the ability to do decent "macro" work. I think the magnification is 1:3 at 50mm, and it can still focus really close.
I think Tamron now has one available with VR (VC, IS, whatever you want to call it), but I don't think that's as important in this zoom range. I haven't missed having it yet with my lens.
Edit: I took too long to write that up...oh well, most is still pertinent.