The Qu-Bd extruder was a pain. The insulation crumbled off, the thermistor wouldn't stay in place, and I had trouble getting either ABS or PLA to run reliably. Everything finally started to work when I made 2 changes - I ground a flat spot on the stepper shaft for the gripper gear's set screw, and I used Arctic Alumina thermal epoxy to install the thermistor into the hole intended for a screw to hold the thermistor. I didn't even bother replacing the insulation - I might, just to keep from burning myself.
With the Acme screw mod, my Slic3r start G-code looks like this:
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G21 ; MM M92 X173.579 Y173.579 Z1515.60 E128 ; calibrate steps/mm ;M106 ; turn on fan ;G28 home all axes
I had a couple of clogs at the beginning of my print - the PLA expanded/compressed in the barrel. I pulled the filament out, cut, and re-inserted, missing ~5 seconds of fill each time. I had this problem with the next few objects I printed as well, but got pretty quick at it. I managed to print the shark (build surface wasn't clamped down & shifted), a gear (fast movements & dual motors at 12v jarred the Y axis repeatedly - very bad print until I upped the power) and both pieces of the Qu-Bd spring loaded filament latch (perfect!).
And a picture: Have fun!