I have it, it is a good lens. In that focal length however, the Leica 60/2.8 Macro Elmarit-R is better. The Leica has no visible distortion (I've noticed some in the Canon), and the Leica resolves fine detail better. For longer, the Leica APO Macro 100/2.8-R is highly rated.
John, thanks for that. Very interesting.
For me, it would be a toss up between the 50mm and the 60mm then. Anything longer would be of no interest.
However, I would like to see comparative tests between them and the Canon 50mm Macro 2.5 or try before buying - unlikely in my case.
Thanks.
D.