I have added comparisons to the following review pages:
Canon EF 70-200mm f/4.0 L IS USM Lens Review - Added a focal length comparison
Tamron SP AF 180mm f/3.5 Di LD IF Macro Lens Review - Added a 180mm aperture comparison
Sigma 17-70mm f/2.8-4 DC Macro OS Lens Review - Added a 17mm aperture comparison