I absolutely adore this lens...but not for macro work haha. Every lens has it's uses and perhaps I'm using mine wrong, but I love the results!
Sharpness: This lens is incredibly sharp and compares to the 135mm L in my opinion
Speed: The lens is a bit slower at F2.8, but the DOF is very narrow and very beautiful giving incredible bokeh.
Bokeh: The bokeh is very soft and smooth with a great amount of separation between subject and background
Price: Although it's a pricier lens, consider that it's a macro lens, can be used for portraits (my main use for it), has IS, is weather sealed and is incredibly sharp. I paid $700 for mine and would never trade it for a 135mm L or anything.
Weight: This lens isn't very heavy at all, the 135 is slightly heavier in my mind. I have it on either my 1D3 or my 6D and it isn't heavy on either.
Contrast: The contrast is pretty good on this lens, but I don't really ever notice issues with contrast on primes.
This is my first post on the new site, but I have over a thousand on the last site, I really wanted to just leave a review and test some things out Hope this is helpful!