The Shapeoko is an open source, 3 axis mill solution. I've ordered and assembled the Shapeoko 2 ala Inventables. The overall kit quality was superb, and the assembly documentation was rarely lacking. The only hitch in the build was that my kit was short three screws, which I may have lost on my own. Inventables' customer service was quick to offer replacements, but I used some I had sitting in the shop instead. Good folks there.
Assembling and tuning took about 8 hours, with most of the time being spent tapping one of 18 forsaken holes in the aluminum "makerslide". I also spent some extra time on the wiring to keep everything tidy. Once assembled, the documentation walks the user through making a coaster with an embossed letter.
After the tutorial part, the Shapeoko gets quite a bit more difficult to use. This difficulty primarily comes from a shortage of easy to use, open-source CAM programs to turn DXF/DWGs or STLs into gcode. There is no magical tool like Slic3r--or I haven't found it yet. Closed-source solutions provide a profound boost in performance, at significant financial cost. :(
Software problems aside, the hardware works great. I promptly upgraded from the stock "spindle" (read: glorified dremel) to the popular Dewalt DW660. The DW660 sacrifices variable speed control for a significant jump in power. And it is completely worth it. The DW660 cuts through acrylic like butter with the stock bit. I haven't found the sweet spot for feeds and speeds yet, but I'm making progress. Once I gain more experience, I'll post the settings that work best for me on the materials I've tried--so far it's just acrylic.
The first few projects for the Shapeoko will likely be upgrades for itself. A dust-shoe and vacuum system to cut down on mess is top priority. I could 3D print one, but I'd rather machine it from clear acrylic so I can observe the tool. Afterwards, I'll be looking towards clamping solutions, and something to regain the Z travel lost by upgrading to the DW660. Eventually I'd like to mill aluminum for a number of projects, we'll get there!