[Klaus]

From the review: 
 
 
 
The lens is designed so that you extend the lens PAST 70mm when attempting close focus shots.  I wonder if the softness at f/4, 70mm, and close focus would be solved by turning the zoom ring further toward the "Macro" mark.  This seems too obvious to be the case, but I thought I'd bring it up in case something was overlooked.
 
The complexities of including the Macro feature probably account for some of the asking price, and make Macro somewhat of a headline feature for this lens.  Therefore it seems odd that there were so many problems with the Macro mode.  Did you take any "real life" sample shots that really exercise the Macro mode?  It would be nice to see how the curiosities seen in the lab translate into real life experience.  
 
EDIT: The Tamron 24-70 seems similarly soft wide open, but this wasn't really mentioned as a problem in that review.  Is there a functional difference between the performance of the Tamron at 2.8 and the Canon at 4?  Is it because the Canon is labeled a Macro lens?  I'm trying to decide between the on-paper flexibility and compact nature of the Canon and the wider aperture of the Tamron, and the RSA/LoCA sections of the two reviews show very similar performance characteristics.

 

Regarding the Tamron - it is basically a standard zoom lens like any other. Most them are soft at close focus distances.

However, the Canon goes officially down to 1:1.4. This is a different marketing statement and as such you have different expectations here. Consequently there is an explicit statement about this here. 

To be fair - the results are obviously very sharp here at f/8 - assuming that you hit the focus point.