After another problem with my Canon 24-105 L I was looking at the Canon 24-70 lenses but several independent reviews actually placed the Tamron 24-70 above the Canon alternatives.
So I ended up purchasing the Tamron lens. My first opinions of the lens are here
First Thoughts on Tamron 24-70 F2.8
And after using it a bit more. It still seems good.
My one complaint, but not something which surprised me, is that it is a little soft at F 2.8. But most zooms aren't at their best when used at the extreme ends. Probably a prime lens would be better for this sort of work.
There are reviews of the Tamron and Canon alternatives here http://www.photozone.de/canon_eos_ff...on2470f28eosff