I get very satisfactory BW prints from my B9180, and have done so over more than two years using PSCS4, PSCS5, LR2, LR3b, Aperture, on various Macs, and under Leopard and Snow Leopard. So there isn't anything inherently wrong with the printer as far as BW printing is concerned.
Calibrating my monitor helped a lot, back when I was getting started with the printer, but I think that reducing the monitor's brightness helped the most.