This lens while being a bit expensive is worth every penny. While being extremely sharp and a constant 2.8 this lens is above any 17-50 lens out there in its class.

Constant 2.8 throughout the whole zoom range

Nothing

For those buying a brand new Canon DSLR I would certainly recommend this over the standard kit lens. Faster glass is always worth the extra investment.

Well-built, wide-aperture, APS-C zoom with three-stop image stabilisation

Peak resolution

Some colour fringing

* Constant f/2.8 aperture * Fast AF with internal focussing * 3.3x zoom range * Image stabilisation system

Peak resolution

Some colour fringing

This lens, even with the EF-S format and inferior build quality, produces surprisingly good images, outcompeting even such "L" lens as 24-105/4 L IS USM. Particularly related to chromatic aberrations which in this lens are neglegible.

Super-sharp images

Poor build quality

The Canon EF-S 17-55mm f/2.8 IS USM is the fastest standard zoom dedicated to Canon's APS-C DSLRs, and is designed to be an upgrade for disgruntled kit lens owners who want better image quality.

Very Sharp and Fast focus lens, crop sensor L quality and was bid 16-35L lens!

This lens is fast and sharp. It replaced a Tamron 17-50 DiII VC. Incredible difference especially in low light. The only thing I miss is the zoom lock, but I can live.

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

Lens Creep

Pros: Fast / accurate auto-focus, Consistent Output Cons: Other thoughts: I've been using a Tamron 17-50 f/2.8 lens for a number of years but really wanted a lens that focused faster and more accurately, especially in low light.

My most shots are outdoor of plants and wildlife. Recently, I shoot some indoor activities, such as musicals, plays, meetings, awards, etc. I use the lens with Canon T4i camera. I am struggling and learning. I had some good shots and some not so good shots.