I'd like some opinions if there are those who use it. I'm thinking of bying it, and as I'm limited with my funds, I don't want to make a mistake. The reviews are very decent and the lens scores high price/performance wise, the photozone.de review was exceptionally good. What can you say about it? Thanks in advance.

a friend of mine has this lens and he's satisfaid because it's sharp and and well built. Autofocus isn't so fast but there's the new model 24 - 70 f 2.8 EX DG HSM (HyperSonicMotor) that you can consider.
http://www.sigmaphoto.com/lenses/lenses_all_details.asp?id=3356&navigator=2
giorgio

I find it a little bit too expencive, moreover - there are no reviews yet, only the price has been announced so far. I wish i could afford the Nikkor. I see one downside of the Sigma - the filter size is HUGE, I mean, 82mm! That's utterly crazy, I've only seen a few other Sigma's with a thread this size, not that I have any or plan to buy more, I'd rather stick with Nikkors if there's a chance. So the filter is clearly not an investment.
Also, the speed, I never found a video with an example in youtube, but photozone, the only real review site that I trust to test lenses, says the speed is decent, altough on the noisy side. The noise is what I don't like, but I think I can handle it.

Some of them have backfocus problem, my Sigma not ... i suggest testing before buying :)

I have both the sigma and the canon 24-70 f2.8, both good lenses but the sigma is a little noisy.

The sigma range nearly all have the 82mm thread, remember that the sigma will stop up to f32 the canon will only go to f22, to most people this is not an issue but I like the facility of f32 for my long exposure work.

Just out of curiousity Mal - do you prefer a smaller minimum or slapping on a filter or is there no real difference on the photograph (not the technique)

good question Kevin. In relation to this thread the sigma sweet spot is around the classic f14-16 while the canon certainly performs well in all situations at f9-11. At f32 you start to run into noise issues especially in low light but this is obviously not an issue on film.

Generally i'm using either the schneider 10 stop filter or the hoya72 ir filter. Typically with the 10stop filter i'm getting exposures of 90 secs at f22 in generally good lighting conditions but using the filter is a pain in the ass (it is opaque to the naked eye) therefore you have to compose the shot, then fit the filter and then usually a 8or4 stop soft grad as well, all while trying not to upset the composition and settings of the camera.

f32 on the sigma does not really cut out enough light to get the sort of results that I like but it has the great advantage of allowing the camera to be used normally and maybe using a much lighter nd filter and soft graduated one and still be able to compose the shot with those filters fitted.

I'm not really into the filters, but I know I'll need the UV purely for protection. I daubt I'll buy any more Sigmas, but this particular one seems to be fairly good, regarding the build quality or images produced. If I'd be using Canon, I'd buy the Canon 24-70 :) although, comparing the tests, Sigma seems to be on par with Canon regarding IQ. Still, non-third party lenses seem to be more reliable.

The Nikkor 24-70 seems to be quite a bit better than both really, but the heftly price tag of 1500$ is unmanageble for a school leaver, apparently. :)

After I've gotten the hold of this baby (I'll test it before buying, of course), I'll be looking for tokina 11-16 - I just love wide-angles! And then I'll need 70-200, but that's gonna be tricky untill I get a decent job, which is altogether daubtfull.

Oh and - backfocus? Hmm, never saw any complaints anywhere, were it some forum or a review site.

Most shops give you some time to return the lens if not happy with it, and so I hope I'll get a chance to test everything. I don't have any software for that though, wonder if I'll have to do it old school.

Finally, art isn't the gear you own, it's the idea and light and colors. So I'm pretty sure I'll be happy with the quality, I know my D80 will be.

I own this lens used on the Nikon D2X, and I am very satisfied:

Pros:
Excellent build quality
Good sharpness throughout the range
Fast AF

Cons:
Beware of flare when shooting into the sun
Zoom-creaping when held vertical
Rather noisy - not a problem when shooting with the D2X, which has a noisy shutter as well.

I use this lens on a ff camera (5d), and it works in a really good way. Considering the Canon 24-70 L I've got to say that lenses quality is not really different. of course, Canon lens is well built and has got a faster motor; and Sigma (on every lens) has got problems of flare, but if you use a polarizer there wouldn't be problems.

I was really dissapointed. I dont recommend you to buy this lens. I Bought it and after 3 months of use I sold it. It was sharp only at F5.6. Better think about Tamron 17-50 f2.8 which is much better. I didnt understand at all why those reviews are so decent ...

You might have gotten a bad sample. Sigma's a lottery. Anyway, I turned down on it and instead am looking for 50 1.4 right now. Not the Sigma :)