rogue_wraith:
Is there a problem with using a Mega? I'm using 33 digital outputs and 7 analog inputs (a number I expect to increase), and trying to avoid adding complexity by multiplexing, since I don't understand multiplexing anyway.
No problem at all, especially if you already have a Mega available. However, the Mega ADK would mean creating a dock with both power and a direct USB connection simpler because you wouldn't need to integrate a USB host shield into the design. It would also be slightly cheaper if you don't already have both a Mega and USB host shield that could be used for this project. To be clear though the Mega ADK has exactly the same number and type of I/O pins as a Mega or Mega 2560, it just has an additional IC chip and USB port to provide the USB hosting functionality.