Canon EF 24-70mm f/2.8 L
Feature Highlights
Lens f-stop range is f/2.8 to f/22 and lens front extends when zooming.
Filter size is 77mm, Minimum Focus Distance is 0.3 meters
at 24mm.

User Rating is 9.3 (out of 10) with over 500 total reviews.

Pros:
The number one most loved feature is the beautiful creamy bokeh behind your subject.  
The nice bokeh comments came from people who did not own prime lens or any f/2.8 lens
before purchasing the 24-70mm
.  The number two favorite aspect of this lens is the
extremely Sharp photos and beautiful Colors.  The number three comment is the fast quiet
motor for very fast focusing.

Cons:
The number one negative comment is people want IS (image stabilizer) features.  The
other negative comments did not appear often, but still are serious problems on all copies
of this lens.  The lens had serious barrel distortion and vignetting issues at the 24-40mm
range and f/2.8 to f/4 f-stop range on full-frame cameras.  These two problems are not very
noticeable on crop-frame cameras.  Another problem is any lens that extends can NOT be
sealed against weather and dust.  Saw several comments about owners taking this lens
into extreme conditions because they assumed all "L" lens have the same weather seal.


Usage:
The most common listed use for this lens is event and street photos.

Conclusion:
This lens works "Great" on crop-frame cameras if you never take it out in extreme weather
or sand storms.  Please note you always take a risk with any equipment in extreme
conditions.  The center image quality is extremely sharp and still usable on the edges.  
The photo edges are almost completely unusable on full-frame cameras for most shots.  
For a lens that cost an average of 1,200 USD, I would expect much better performance on
a full-frame camera.


Source:
Fred Miranda Product Review