Just backed the Zero Pi project on Kickstarter. Looks like a cheap and easy way to build a Raspberry Pi based 3D printer.
I like that this opens up the potential for WiFi access with an integrated onboard web-server. This is the perfect combination for the Fabribot 3D printer that I am developing where browser based printer control is something that I would like to achieve. Imagine: Just open up your browser, navigate to your printers IP address. Upload a file and print. There's even the possibility of integrating onboard slicing - where you can send the printer an STL instead of G-Code. It's all pretty easy to achieve with a Linux based controller and a simple web interface.
From what I understand there's a communications abstraction layer between the Arduino and RasPi aspects of the system, both of which also operate independently. This communications layer allows you to access Arduino I/O & variables from within the Linux core and vice versa. The actual details are a little unclear but for adding a simple web interface to an Arduino an leveraging the power of linux to take care of file handing it seems to have all that is required.
I'm pretty excited about this. Guess now I need to get my game together and finish off the Fabribot