boss = bad tracking.
i've heard nothing but good things about the digitech bsw... as far as octaves are concerned.
i own and love the POG. it was fascinating when i bought it, and it's still fascinating a year later.
haven't heard the octabass, but heard good things.
i've heard that the mutron and the qtron were both designed by the same person (EH actually designed the qtron, but under the guidance of the original mutron designer). i have a qtron+, and the sound is amazing. never tried the mutron personally, but i've heard it's absolutely The Bee's Knees.