I just completed the auto-focus test on the 100 and 180 Canon Macros and I've concluded that auto-focus on Macro lenses is a complete waste of my time.
I've also concluded, if you plan to use either the 100 or 180 Macro for portraiture (anything more distant than a head, neck, and upper-shoulder), expect the eyes to be out of focus on ALL your frames, no matter what the f-stop. After all, these are Macro lenses and, unless you're very close to your subject, the eye socket is too small a territory for AF to catch. Not to mention, I'm on a tripod, using a shutter-release cord.
Utilizing every AF Point that the 5D offers, none of them brought home the bacon on the more distant portrait. Furthermore, I can't tolerate composing my image to accommodate any camera's AF Point. What kind of photography is that? Even with the Ee Diopter Screen in my 5D, on Manual Focus, I could NOT get the model's eyes in focus from a distance. Every time I took a portrait that included head, torso, and hands, the eyes were NEVER in focus.
I imagine if I was tethered to my computer, I could probably get there if I kept tweaking. But, frankly, there are far better lenses for portrait work that waste much less time and provide spectacular results. Unless you're broke, why use a Macro for non-Macro portraits?
Now, when I brought that 100mm baby closer to the subject (face only) and manually focused on one eye, the results were MAGNIFICENT. Absolutely incredible. Every lash, every pore, and the reflection of the daylight window in the pupil as clear as glass. The bokeh was sublime. I was REALLY impressed, especially at 2.8, even more so at 3.2.
Macro lenses are designed to shoot close and nothing can take the place of a good Macro. That's why my next lens purchase will be the EF 100mm, 2.8. I'm getting really excited.
ps Now if only you didn't need two weeks lead time to rent the 85mm 1.2L in NYC. The results of that test will be coming as soon as I can get my hands on a lens.