rik: that ultraman work looks great! yes, cleaning the bitmap up BEFORE processing is a very important step. If you have clean bitmaps, the resulting vector is fairly painless. Removing all the blowholes and stray pixels is not too tough if you select all the black areas in groups and just dump black in there. If there's any greys they get wiped out. I do a final conversion to 2 colour bmp and then clean up after that.
the edges are well defined and straight so I don't see why that wouldn't work well.