Given that the Leica I've been using lately is a macro lens, I thought perhaps I'd do a quick and dirty test to see if it's useful in that realm. I should warn you that this test is likely even less rigorous than the others, since there are many things that can go wrong when magnifying a subject by this much. I used a simple method. I set the lens at full magnification, which is to say 1:2, mounted it on a tripod pointing straight down, and then adjusted the height of a Euro coin so that it was in focus. Without macro rails this was not as easy or accurate as it should have been.
Then I took shots using the same aperture settings as in previous tests: f/2.8, f/4, f/5.6, f/8, f/11. I used natural light and longer shutter times, in order to avoid extraordinary specular highlights. The image here is cropped square to eliminate background but is otherwise untouched. All the shots are available in 1200 pixel images on Flickr. This is only the f/11 example.
My summary of the quality of the Leica lens is exactly the same as at other distances. Wide open the lens is definitively soft but through f/8 it is consistent. Then f/11 shows a drop in sharpness. That is compensated for here by the fact that f/11 was needed to bring the whole coin into sharp focus. Obviously the lens was not exactly perpendicular to the coin. That's just one of the factors that is difficult to control without a more formal test setup.
As a comparison I made the same test with my Vivitar Series 1 105mm f/2.5, a lens I very much enjoy and which produces excellent real-world results. I set it also to 1:2 but of course the magnification is greater due to the greater focal length. Thus it is impossible to do a strict comparison. The exposure also came out quite different. Nonetheless this comparison is sufficient to realise that the quality of the lenses is quite similar.
In conclusion, I do wish the Elmarit maintained its sharpness past f/11, because otherwise three-dimension objects will have only a very small depth in focus. This is compensated for by the shorter focal length I suppose, but that has its own disadvantages, in that it is often better to have more working distance (doesn't scare bugs or cast a shadow as easily).
Nonetheless I have no complaints about the Elmarit's performance in the macro realm. It appears to be a solid performer, with identical characteristics at all focal distances. In fact it could be said to be a jack-of-all-trades, not sharp enough at small apertures to be a perfect macro lens and not sharp enough at large apertures to be the perfect portrait lens, but excellent in the middle realm of f/4 to f/8.