Pros: Wide, great color, great sharpness

Cons: Won't work on a full frame body. Of course it's really 16mm on the wide since it only works on crop bodies.

Other Thoughts: This lens is the reason I keep my 7D body after upgrading to a 5DM3. If I want to shoot landscapes I prefer the images from this lens over my 24-105L by a long shot. You can't go wrong with this lens.

Pros: Outstanding zoom ranges, good speed and built, very sharp pictures with good color retention.

Cons: Still needs tripods for shooting night scenes. A VR version may help

Other Thoughts: The canon 10-22 ultra wide lens has been out for quite a few years, however, the performance and built had been amount the best. I have also the 24-105L and 100-400L lens, I am surprise to say that in many cases, the 10-22 seems to be sharper than the 24-105L (of course I am comparing apples to oranges due to the different lens coverage). I was able to share filters as they all use 77 MM filters. More importantly, I found this zoom lens with my 60D (1.6X) very useful for indoors, architecture and landscaping (which comprise of almost of 80% of the situation. The distortion at the far end is quite acceptable and even portraits come out great (as long as they are in the center 2/3 of the frame. At wide ends and if subject is placed at corner, it can look quite distorted (can somewhat be corrected with canon software). The colors are well saturated and flare not much of a problem. I found if I am only allow one lens to take with me, this is it.

Pros: Excellent quality, Ultra wide angle on crop sensor cameras

Cons: It does not come with hood!

Other Thoughts: Great buy!

Pros: Excellent quality, feels very durable.

Great for real-estate photography or artsy angles on an otherwise bland subject.

Wonderful super-wide angle alternative for people who aren't ready to spring for a full-frame DSLR (me).

Super-quiet focusing... can hardly hear it at all and it's lightning quick and accurate.

Cons: For beginners with too much money: this lens will only work on a "cropped-frame" DSLR. (Canon Rebel up to 7D, won't work with 1D or 5D)
I'm not familiar with the Nikon equivalents.

Distorts in the corners, but it's a super-wide angle, so that's expected.

Other Thoughts: If you plan to upgrade to a full-frame body soon, it might be wise to wait before purchasing a wide-angle lens, since this one is limited to use on the cropped-frame sensors.
If you've got a Rebel or other cropped frame camera and you're perfectly happy with it, you will not regret purchasing this lens. It's absolutely perfect for what it was designed to do.

Pros: excellent lens for interiors ,wide landscape and night

Cons: none for optic , price far too high for non IS lens

Pros: Will first start off by saying I am a new photographer so my tech level will not be as high as many of the reviews here.
With that in mind here are my pros:
1.) This lens will add an entirely new element to your photographs. The shots you can pull off with this thing will amaze you! Sitting on the ground last night just messing around I was able to capture my feet and the top of a 4 story building in the image. Moving on to street scenes the shots I took just felt like they had so much life to them.
2.) Its FUN!!! Mess around with it, try different focal lengths. Be creative and dont worry about what the finished result will turn out to be. Let the lens take care of that.
3.) Reviewed the pictures I took yesterday and did not see any soft edges at any range. But I typically hit a stop and back off just a hair so this may be why.

Used this on a Canon T2i and it is the second best lens investment I have made.

Cons: No lens hood ??? Not a deal breaker but would have saved me from another purchase. GET A LENS HOOD FOR THIS BAD BOY!!

Other Thoughts: Newegg had this to my door in under 2 days.
Pictures are sharp and the reviews say this is as close as you can get to an L lens without the price.
A bit pricey but hey isnt everything we buy in this field?
BUY THIS LENS AND HAVE FUN!

Pros: Compact and light weight. Surprisingly little distortion for an ultra-wide zoom. Reasonably sharp. Fast, accurate ring USM focus.

Cons: Same price range as the 17-40L without the 'L' build quality.

Pros: Good: Superwide angle lens for Canon DSLR. It is not as fast as the Canon L series lens. But it produces a good optical quality for such a price. Some distortion and chromatic aberration at superwide angle. But it is usual for superwide angle lens. I am very satisfied with this lens performance so far.

As far as the services from Newegg, I have no complaint yet. Keep up the good work, Newegg team. Thank for your services.

Cons: Non so far.

Other Thoughts: Prior to buy this lens I also considered the Tokina 11-16mm f/2.8 and the new Sigma 10-20mm f3.5. However, I leaned more toward the Tokina since it is a faster lens with constant aperture at f2.8. It produces the best optical in its class. If Canon choose to made the same aperture as the Tokina, then they would probably sale under L series which would cost at least 2-3 time the price. However, the Tokina has less zoon range than the Canon and it might have the compatibility issue with Canon future product. It took me a very long time to decide between these two great lenses, Canon and Tokina. I like the Tokina, but I buy the Canon for my need. So you have to decide what you need.

Pros: The best small sensor wide angle lens in Canon's lineup. It's quiet and it focuses quickly. The clarity of this lens competes with that of many of the L series USM lenses.

It suffers less barrel distortion. Flare is mitigated in this lens far better than in most USM lenses. Plus it has a circular aperture design.

Cons: Canon lenses are expensive. It doesn't work on a full frame body.

Other Thoughts: If you have a small sensor canon DSLR get this lens. You won't regret it.

Pros: Fantastic All Around Lens, literally converting your APS-C sensor into a 35mm equivalent camera. Excellent optics for how old this lens is, clean and sharp image. Literally, this
lens will become your favorite all around lens. This lens completely satisfied my need for a full frame camera (for now).

The build quality is fantastic, I was honestly amazed at how solid it is, I was expecting a cheap and loose USM build, equivalent to the 70-300 IS (not the recently released version).

Cons: For a 15mp+ sensor, you still will be dismayed to know that there is still no EF-S lens out there that takes full advantage of the bigger sensor cameras. This translates into loss of detail at higher crops. The picture is clean, tack sharp, and detailed at up to 25-40% crop but from 50% on up (if you are a pixel peeper) you will notice that some detail is not captured that maybe would be with something like an L series lens. On the contrary, nothing out really takes complete advantage of these sensors.

Other Thoughts: This lens will remain in my collection forever. Definitely one of my Canon favorites! It rarely ever is detached from my camera, unless, I require a longer reach.