Digital BW, The Print

With Epson's ABW driver you can convert an RGB color image to b/w
right inside the driver. You can let ABW print it "straight" or add a
warming or cooling tint. This printer driver conversion will be
different than if you convert it yourself in Photoshop. You've got
lots of ways to do the conversion in Photoshop, from
Image>Mode>Grayscale to harnessing the myriad of options in
Calculations. And CS3 offers a new and much more intuitive method.
The downside to using ABW is that it is not color-managed; you can't
see onscreen exactly how the image will print, as you've discovered. A
$50 solution is to use Roy Harrington's QTR. With his software and an
Eye One spectrophotometer you can soft proof a grayscale image and
print it through the ABW driver with a custom profile.
-- 
amadou diallo
Author, Mastering Digital Black and White
www.masteringdigitalbwbook.com