While we are concentrating on supporting PLA as the primary printing material (most people prefer printing with PLA) it should be possible to print with other materials as well. The main issue is that without a heated bed, you have to do a little surface prep on the build platform to get things like ABS or Nylon to stick. We have done some test prints with both ABS and Nylon, and there were no particular issues with the extruder. It's not an all-metal extruder, however, so the temperature will be limited.

As for spool location, the plan is to have it fit behind the printer. While it would look really clean to have the spool integrated into printer itself, this also makes it a bit of a pain to change filament. We envision that users will want to play a lot with different colors, and having to fish around underneath the printer to change the spool is inconvenient.