Without a doubt the goofiest looking machine I have ever seen. Seems to work though, at least with a pen.
look for file:
The Adventure Of Building A Delta 3D Printer circle fast RWGresearch.MOV
Hopefully I'm wrong, but when you add the extruder head and filament attachment, I can't imagine it holding stable at the speed you were drawing with. Seems like it would clank and bang all over the place. That is a lot of momentum hanging out there on just six little arms. I think while you are still working on leveling the bed and using a pen, I would attach an equal ounce weight of the extruder head to the mount point and just solid mount your filament line, then try some more runs with that extra baggage and see how it does.
Also, how are you planning to compensate the filament line as the head moves around? Won't you be pushing and pulling on it constantly?
One other thing I just thought of... If you think you might be doing any jobs longer than an hour, I would definitely consider getting an online UPS to power it. One little power glitch and ten hours of work (plus materials) would be lost. I'm using an OptiUPS online UPS with my CNC router. It also runs my shop computer that drives the whole thing.