Are you looking for third party lens alternatives? Take a look at this selection by DPReview.com:
Ever wonder how to check if you lens is a good copy? Check out this in-depth look at testing lenses from LensRentals.com:
The Sigma 18-35 mm F1.8 DC HSM A lens has some impressive sharpness score, even beating the Canon EF 24-70mm F2.8L II USM!
The only things lacking is the focal range and stabilization. See the article from DxOMark below:
Sigma’s new 18-35mm f1.8 zoom lens looks good on specification and on price too! Certainly a lens to watch.
Sigma’s Game-Changing 18-35mm f/1.8 Zoom Lens to Cost Just $799
As an industry first, Sigma has planned to release a USB Dock for customizing their lens
You can determine the age of a Canon Lens based on the serial number and date codes
For Canon 5D Mark III owners, have you wonder which lens to purchase to make the most out of the camera? The following article from DxOMark might give you some insight