I've been using it as my primary wedding lens for a few years now, it's a very capable lens. The new version with VC (Tamron's version of IS, VR etc.) looks very promising as well, but it a bit more expensive.
I don' think, however, that it will be any better than the 16-35mm F2.8 L. It's only advantage being that's it's less than half the price.
The Canon EF-S 17-55mm F2.8 IS, is certainly worth considering. It's a better lens than the Tamron, but it's twice the price (of the non-VC version anyway).