Using a test chart, I found the lens to be very sharp across the image at all focal lengths. The included picture is typical of my results and is a small part of the image from a Canon 5D Mark-II.

The lens quickly snaps into focus and produces good closeups at the 40 mm setting.

Fast / accurate auto-focus; Lightweight; Sharp at all focal length

Barrel distortion

I was surprised to get an "L" lens at this price. This one definitely deserves the "L" in build and optics. It'd been my go-to lens since I bought it in March. Each lens has its odn personality, and I really like this one. My clients like it too.

Consistent Output; Durable; Easily Interchangeable; Quick Focus; Rugged; Sharp Focus; Strong Construction

Heavy

I use this lens for shooting abandoned buildings, so I can more get the scope of the place I'm shooting. THe only thing to keep in mind is that this lens is an f4, so there are some speed and low light issues, but if you're using strobes then it's not a problem.

Strong Construction

Poor in Low Light

The only thing I would comment on is that there is not enough "blur" for some portraits, but I knew that when I bought it. It produces great pictures! The clarity is wonderful!

Easy To Use; Good price value; High quality pictures; Quality Construction

It is use in 600d

Well worth the money compared to McBain's pricing,!!!

Smooth operation, and a great upgrade for the standard lens provided with the T3I Canon; Great clarity

A little tilt on the vertical structures; but acceptable

I love this lens. Nice color reproduction and fast focusing. Gave me great results in my last outdoor photo shoots!!

Consistent Output; Fast / accurate auto-focus; Nice Bokeh; Strong Construction

I recently switched from Nikon to Canon and this was my first lens purchased for my 5D Mark II. My decision was made after reading several reviews from websites and blogs. I have to tell you they are all right! This lens takes sharp and vibrant pictures. Good bokeh too, though not the best.

Excellent lens, as expected for an L series lens, Very light

Great sharp lens!