Most of the reviews I've read have noted the 50mm macro as one of the sharpest lenses they've ever tested on a DSLR, so I'm not sure where that comes from... it certainly outresolves a 10mp sensor. As a macro lens, though, AF is less than thrilling.
For most practical macro work, however, one of the biggest drawbacks of the 50mm is the working distance; you have to get pretty close to the subject. At the moment, Sigma offers a 105mm 2.8? macro that has a good reputation, and the 150mm 2.8 macro I currently lust over. Both are known to be very sharp, and fairly well built (though not sealed like the Oly glass). As macros, of course, AF is still iffy, but focus limiter switches help.
Looking to the future, there's an Olympus 100mm macro (either f2 or f2.
on the lens roadmap, expected to be announced in September this year. It will no doubt be a very capable lens.
