The Quantaray/Sigma 28-90 arrived today, so I put it to a few tests against my well-liked Promaster 100mm macro. Both do about 1:2 closeups in native mode; the Promaster includes a 49mm filter-type multiplier to achieve 1:1 but I seldom use it, so 1:2 seems sufficient for me. The lenses don't compete on speed, since it's 100/3.5 vs 90/5.6, but what the heck we'll put them head to head anyway.
A few quick tests at 1:2 were not definitive so I shot the neighborhood to see the results. In the climatis-and-mailbox shot the Q-ray image was decidedly better in exposure, avoiding the major blowout of highlights that the Promaster displayed. Just a single shot but a clear difference. Looks like a flower horse, but truly it's not!
Later I shot a closeup of our porch post with many things behind; both shots have rather nervous bokeh on display, so again no clear victor. I shot these through a window, which helps neither lens show off to its best effect.
Let it be noted that the Q-ray focus is slower and feels more precise, and it covers its full range in about 1/4 turn. The Promaster nearly goes full circle, meaning if it misses you'll be waiting a while for it to get close again. Enough victories that maybe the 100mm will be sent packing.
In the wide department the same could happen with the Sigma 15mm fisheye. It takes some excellent and fun images, but the 17-35 Tamron non-fisheye is clearly a winner and both are f/2.8 - still counting votes on the result there.