Well, I'd just about had it with my MakerBot's Idler Wheel; It keept ruining prints by separating from the bearing and letting the filament slip to the side, away from the extruder's drive wheel, so I decided to upgrade. I bought an aluminum idler wheel on ebay for $15 + $1.50 shipping (search for "reprap"). It has a groove cut in the side to keep the filament from slipping oast the wheel, and it has the bearing press-fit into the idler wheel, so the idler wheel will never slip off the bearing and slip past the filament! It's been running well during the prints I've been using it, and has made changing my skeinforge settings easier by making the MakerBot's extruder much less dynamic and much more reliable. I have also recently switched to skeinforge 7 from skeinforge 5 so I could use the new raftless plugin with PLA.