The Sony 24-70mm f/2.8 is probably the only fast std zoom lens that is good. I don't expect anything from the new Sigma and Tamron.
But then this is a useless lens category - not really fast, excessively heavy and big, very expensive relative to what they offer. PERSONALLY I couldn't care less.
Something like the Canon 24-70mm f/4 makes more sense.
But we are all different.
Ah! Then I'm not the only one who thinks along these lines. Never had a 24-70/2.8 class lens - I thrive on the 16-35 + 70-200 combo, and in the middle I got the humble 24-85/3.5-4.5.
Incidentally, I had conflicting thoughts on the issue when I was shooting a wedding a couple of days ago (to put the record straight, I'm not in that business but I was doing this for a friend). I was mostly using the Canon 24/1.4 and 50/1.4 lenses with 70-200/2.8 IS added for good measure, and found that while I could have a decent hit rate, a lot of the time I wasn't having nearly enough DOF when shooting between f/2.5 and f/4.5. For proper DOF I would have stopped way down to f/11ish and pulled focus, but the proceedings were taking place in a church (thankfully, there was quite some natural light from the windows as the weather was good and the time, well, about 2 PM) and so I would have had to go to about 5-6K ISO, which I could not afford. I can imagine that many wedding shooters are facing a similar conundrum whenever they can't use flash - then, of course, it'd be f/11 and a controlled exposure.
Just like I ditched the 16-35/2.8 for the 16-35/4, I would prefer a high quality f/4 lens in the midrange as well. Oddly enough now I appreciate the 2.8 aperture on the 70-200 so I reconsidered selling it. However I'm content with the 24-85 for now as the real gap is only from 35 to 70 which is not a big deal...