I went to the PMA exhibition in Melbourne today and got to play with the new 24-70mm f/2.8 II USM and I gotta say I was really impressed with the size, build quality and focus speed. Can't comment on IQ ans I couldn't take images away.
If you look here http://camerasize.com/compact/#312.289,312.286,ha,t
they have it wrong - the mark I is about right, but the mark II - there's no way it was that big next to the mark I. I took my mark I lens in with me and held the two size by side and the mark II is substantially smaller and lighter, which put a big smile on my face, as I find the mark I just a bit too big and bloated - especially the fat lip at the end. The mark II seemed just right - like a 24-105mm - very nicely balanced on the 5D3 body (no I don't work for Canon!!)
Some other observations:
1. Hood. Damn I love the lock-in hood! I've shot weddings where my mark I hood has turned a little (mine's very loose) and I've got the black hood in the corners. The mark II hood snaps in with the same firmness as the 70-200 f/2.8 IS II USM - inspires confidence.
I do like the smaller hood immensely. I shoot landscapes with filters a lot without hoods and find that flaring is very rarely a problem. I think with this hood - sure it won't be as deep as the mark I but in reality - I can't see that as being a problem at all.
The only time that I prefer the old hood is when it's raining - the front element has greater protection, as does the lens extension barrel.
2. Focusing. zing! super fast! Really though I don't know how much of that was the 5D3 though. I wasn't allowed to put the new lens on my 5d2.
When comparing side by side, the old lens focus has a lot greater distance from 1.5m to 3.0m to infinity. I'd roughly put it at 1.5 times the turning amount to go from 1m to infinity on the old lens. The new lens - gonna make it a bit harder for manual focusing hitting the right hyper-focal distance as the markings are so close, but the trade off is most-likely to be the faster autofocus.
3. Build quality - no complaints. The big amount of rubber is nice to handle.
4. zoom feel. The old lens feels loose-ish around 70mm and tightens around 30mm and requires a bit more force to twist it to 24mm, whereas the new lens feels more even in tension throughout the zoom range.
Not sure what else I can tell you. If it was a choice of saving size and weight with no IS, or keeping the same size and weight and adding IS, I'm glad they went with no IS and gave me the weight and bulk saving that I'm really happy with. (remember IS does nothing for a moving subject!). To keep everyone happy, they really should release an IS version of this lens though.
It'll make for a great all-rounder lens. I think it will be fine for street. Not as good as a 50mm f/1.2 or 85mm f/1.2, but a lot better than the 24-70mm mark I due to the smaller size, which makes it easier to whip out of the shoulder bag.