A 17-55 MkII would be nice, but I think I would stick to my current one. It's still a perfectly good lens, sharp and fast, and I have no problem with the current build. I will probably end up using it until it dies on me.
I'm looking forward to seeing reviews of the new 15-85, though. If the IQ comes close to the 17-55, at $800 it would be a steal. The focal length range is perfect for 1.6 bodies, and the variable aperture can be forgivable if the IQ is up there. If I'm reading them correctly, the MTF charts for the 15-85 look slightly better on the wide end, and slightly worse on the tele end than the 17-55. It's comparable, so it looks promising.
Indeed, Especially given the pretty good AoV increase at the wide end [24mm vs 28mm is a good difference!] if it holds the corners well...
I'm actually interested in flare performance, the 17-55 did not do so well with this for me sadly...I'm curious to see if the 15-85 does better [Maybe some better coatings in there..]
The optical design and glass used seems VERY close to the 24-105, 3 aspherical + 1 UD in the 15-85 vs 3 aspherical + 1 S-UD...The 24-105 would be harder to correct optically given its larger image circle and constant aperture mind you...So from a technical standpoint, on paper, the 15-85 seems to have the goods...

But that was my 200mm f/2.8L which IS weathersealed...
I hope the haptics will match the looks.
