I tried printing a couple more objects today.
I managed to get a complete MakerBot coin printed. It looks pretty good. After that, I tried to print a dodecahedron. Unfortunately, the machine stopped extruding part way through the print each time I tried.
I think the extruder motor keeps going, but the pulley digs a notch into the filament instead of moving it. I might try tightening the idler wheel a bit, but I'm wary of breaking it. Maybe I should check that the extruder is still hot when it stops extruding; if for some reason it's cooling off, that would certainly make the filament too hard to extrude.
Here's the completed MakerBot coin, and a partial dodecahedron: