Omg, I cannot believe it - After a long wait, my first L grade lens has arrived! Italian customs is a big problem to work with, they held my baby in fedEx office for two weeks 
I’m very excited to test this lens in a real world environment under practical use. So this review won’t cover any technical issues; there will be no charts, graphs or any other measurebating comparisons. I’m sorry but if you are after this kind of information I advice you to look somewhere else
Build quality of canon 17-40, like of any L lens, is amazing. It is also very nice to handle - Zoom ring is smooth, and full time manual focus ring is also comfortable to use. 17-40 isn’t very heavy, thus it makes a very good walk-around lens. I know some of you would say this range isn’t good for all around lens. But on a crop camera range increases to 27-64 and in practical use I find it very satisfactory for street photography.
Another issue might be a slow aperture, this lens is full time f/4 - Personally I don’t find this to be a limiting factor considering it’s use. This is Ultra Wide Angle lens meaning you want to use it for landscapes, architecture etc. and no landscape photographer shoots bellow f/8.
Quick Tests
I also decided to do some quick sharpness tests, nothing special just shooting around in my room.
Sharpness @ 40mm f/4.0 is decent as expected.
100% crop (Center)
I’ve read on several forums that 17-40L performance isn’t quite good at the long end. Frankly, I cannot confirm this.
Sharpness @ 17mm f/4.0 is excellent.
100% crop (Center)
Real world TEST shots
17mm f/4 Downsized full image.
Center crop (100%) from the test landscape shot.
Same crop with a bit of sharpening applied in Photoshop.
Where to buy
I bought 17-40 f/4L from Ebay, member: Sighterz
I highly recommend this guy: his pricing is decent, he ships internationally (package arrived in less then 3 days) and the best of all he knows the trick how to avoid import taxes 
As a bonus you also get 8 year international warranty. If you buy from Sighterz Lens comes with hood, pouch and UV filter.
Update: 2008
This lens is amazing! Check out reflections on this car… full view please.
24mm f/4
17mm f/5
I’m very confused about performancec of 2 lens.
1. 17 - 40
2. 24 - 105 IS
Focal length is not a matter, I want only exelent immage quality.
which one is best for my EOS 350D ???
I used the 16-35 L mark 1 for a few years, and have been using the Sigma 15 - 30 EX for a few more years. I considered the 17-40, but I don’t like the slow aperture ( even for landscape photography, which is usually in the f/11 to f/16 range, I like a bright view finder, especially for night work ) and 17 mm isn’t really wide enough for my taste.
Personally, I’ve been lusting after a 24 mm f/1.4 L. I realize that’s significantly narrower than 17 mm, although 24 mm ( on full frame ) is a magical field of view. Just incredibly well suited to landscape photography.
Ironically, an ultrawide is the only zoom I have. The rest of my lenses are generally L-series primes. If you ever get a chance to use the fabled 135/2, it’s painful to remove from your camera…!
bhaskar mitra » Well in general it only depends on the use, if you aren’t a landscape photographer UWA like 17-40 won’t serve you well. 24-105 on the other hand would make a perfect walk-around for any need. Image quality is excellent, IS is very helpful etc. So I recommend taking the second option.
Forrest » 24L is a beautiful lens, I had a chance to rent it. Well I don’t do much of landscape photography, but for photographing people in their natural environment as a street photography style its perfect for me
You’re a little too enthusiastic.
OK, it’s a good lens but an “L” lens doesn’t really mean anything. You could get beautiful results with a cheap 1960’s lens with an adapter.
Naive beginners think all these wonderful things about “expensive” lenses, but they don’t have the experience to make sound judgements.
Stinky » Sorry, but you are very wrong. L lens means several things, that is excellent optics, outstanding build quality, blazing fast AF, and sometimes weather sealing. On the other hand I agree, there are some gems among old lenses that can be comparable. But then again buying lenses from 1960’s doesn’t make any sense, since you loose AF, AV reading, using adapter also causes some lenses to loose infinity focus. So paying extra for a brick (L) that will last you decades isn’t such a bad idea.
Also note, this is the least expensive L lens. Seems like you don’t know much about canon line-up and specifically L lenses. I suggest you to do a little research on the subject, and then maybe we can have a discussion here
p.s. At the end of the day, its the photographer who takes photos, and gear doesn’t matter much!
Nice review and photo’s - This will be the first lens I will purchase to go with the 30D I have my eye on!
Thanks