[toni-a]

I tried this lens last week on 7D2, I am not going to discuss image quality Klaus did an excellent job already.
The question is does this lens make sense ?
it was a joy to use except for two major things: size and weight...it's really heavy, Canon 17-55f2.8 is much lighter and shorter in comparison !!!!
In Fuji mount for instance it would take practically  same space in bag and have the same weight as 18mmf2 plus 23mmf2 plus 35mmf2....
So my humble opinion: if you are doing video and want to zoom while shooting, it's a must have, an awesome lens by all means. however for photography a more compact and better range 18-50 would make much more sense

[Klaus]

I reckon Sigma will release a more compact version eventually.

That being said ... a 18-35mm f/1.8 is a FF 27-53mm f/2.7 ... once you inhale this, it's not THAT special anymore.

[Rover]

It's still 1⅓ stop faster than the common alternatives for the same format. Either you're in need of this, or you ain't.

[toni-a]

For still images it's not THAT special as Klaus said regardless of optical performance , however for video it's a very handy addition

[Klaus]

It's still 1⅓ stop faster than the common alternatives for the same format. Either you're in need of this, or you ain't.

Yeah, but by doing so you are taking away any weight/size advantage of the smaller formats.

The only argument left is ... "I own an APS-C camera".

[Rover]

Which I think is a compelling one for someone who actually does own it?.....
Heck, I was thinking about the 18-35 and 50-100, and I have a 1D. :-)