First of all I am really excited to see this kit. It simplifies and makes permanent something I keep needing to redo for different projects, adding an LCD screen and some buttons to work with. That I only need to use 2 pins is just icing on the cake.
I am currently playing with Arduino, Netduino, and will soon have a Beagle Bone. The last two run at 3.3V, from a hardware perspective is there any reason that this shield can't be used at 3.3V?
I read the data sheet for the MCP23017 and couldn't find any reason it wouldn't work. The only limitations for 3.3V I could find was a bus speed of either 100 kHz or 400 kHz and the temperature must be less than +85 C. Am I missing anything?
I realize that I will need to write my own libraries for Netduino and BeagleBone. If I can find the time to make them professional, I will put them on GitHub. No promises, since part of the fun microcontrollers is that they isn't my day job and the code doesn't have to be professional.