9 out of 10 points and recommendedlight, well build, near silent OS, superb opticsfocusring does turn and no full time manual focus
I was waiting for this lens to become available as I was looking for this type of lens for shooting weddings. I also looked at the Canon 17-40 4.0L and EF-S 17-55 2.8 IS I was very interested to see how well the new FLD glass would perform after reading very good reviews of other lenses with this type of glass. After comparising the lenses I dropped the Canon EF-S 17-55 2.8 IS from my shortlist mainly due to the high price and less than stellar build quality. The 17/40 4.0L is an impressive lens with stellar build quality but does not have IS. I do consider IS and 2.8 as a bonus as light conditions during weddings can be very troublesome so having a 2.8 lens can help focussing (also 2.8 means high precision AF) and IS helps to avoid camerashake so I can use slower flash sync speeds to get a more natural looking picture when flash is needed.reviewed June 24th, 2010 (purchased for $765)
So I went home with the Sigma and boy does it perform... It is stunningly sharp even wide open and it gives me very clear, brilliant beautiful pictures with great microcontrast. It has the same brilliant high quality picture feel as for instance the 70-200 4.0 L IS
The FLD glass sure is doing a great job as abberations are almost completely absent as is purple fringing that can be a pain on these wider lenses (my Canon 20-35 has very high levels of it) I did take a picture of a military chopper against a very bright sky and there is none aberation visible... Compared to my Canon 20-35 and even my Sigma 24-70 2.8 HSM it has clearly beter optics as also the distortions are well controlled. Bokeh quality is also good, it has rounded blades which give a nice even background blur.
Mechanicaly it was suprising to see a rotating focus ring on a EX lens. I guess it is done to keep the lens as small as it is. ALso full time manual focus is not available. Both points are a pity as it would have it made mechanical and ergonomical even better. The AF is on the other hand very precise and fast, I had no problem tracking cars that where doing 70kph. The OS is the best I have seen from Sigma yet, it is completely silent (in fact I had to held my ear on the lens to hear it as I thought that it did not work) It is also effective. There is no play in the zoom and focus ring and the tube when zooming out to 50mm has no play as well. Although being light it does have a quality feel about it as to be expected of an EX lens. The swithces are precise and have a nice click to it, a definite improvement over earlier lenses.
So all in all I am very content with this little marvel and I am looking forward to do my first weddding shoot using it.