Well, embarrassingly, I mistook a FIFTEEN ohm resistor for a 1 M resistor... So all my guitar signal was merrily diverting to ground. I've got the thing working now, but my power supply is buzzing nastily. What I can hear sounds cool though! I'm running my 12v ps into a little rc network ps filter that I built, but it doesn't seem to be helping a lot... anything else I can do to clean up the nasty hum?
EDIT: Goodness gracious, apparently I need to increase my caffeine consumption if I'm going to be attempting anything electronics related. I forgot to ground the freakin ground bus that the guitar jacks were hooked to.
Everything is working optimally now, and this thing sounds beautiful!!! I'm totally sold on this circuit, and I plan on building a pentaboost --> valvecaster build very soon!!!