I just picked up a used Subterranea from the classifieds here and hot damn!! This thing slays - absolutely blows out of the water every other octave and/or synth type pedal I've used. I swore by my Octron for years, but I'll be selling it shortly, I fear. The Sub-T has such a rich harmonic content and a lot of cut built in - no need to stack drive or fuzz pedals after it, though it's still fun to do that. Currently really digging a 50/50 mix of the Octo synth on triangle and Uni Synth on square, with some Octave blended in; I don't really need the clean blend for what I'm doing right now. Run this combo through the MXR BEF, and I'm loving it.
EDIT! Forgot to mention that the Sub-T tracks all the way down to G for me, sloppy technique and all. Amazing.