I (Philip Mathieu) have been working with my brother (Nathanael) to adapt OpenROV for the Raspberry Pi. We've had a lot of technical difficulties, gone through three different Linux distributions, and learned a lot along the way, but haven't quite managed to get everything running. That being said, the most important components (working out the power wiring, getting the UART properly configured, etc.) are all working, and we hope to have a fully functional OpenROV-Pi in the next two weeks.
A lot of the trouble with the Pi is that there seems to be no way to program the atmega328p on the OpenROV Cape through UART. (Josh Borisoff was able to successfully upload to the chip itself by pulling it and connecting over SPI, and lots of users (on BeagleBone as well) have successfully uploaded by swapping the chip into an Arduino Uno.) Here, the main problem seems to be with configuring the reset pin properly - a problem that may be similar to what BeagleBone users have struggled with.
Powering the Raspberry Pi turns out to be as easy as wiring the right pins on the Cape; additionally, wiring solely the 5v and ground pins powers the Raspi properly so that it can provide 3v3 from its own headers.
Finally, software. Most of the code will run properly with minimal changes (editing config.js to reflect the Pi's serial port /dev/ttyAMA0 and commenting out the setuart.sh script as the Pi has UART setup by default). At various points we worked with the Occidentalis, Arch Linux ARM, and Raspbian distros, and ultimately chose the latter after a couple weeks of experimentation for simple logic:
Ultimately the long story short is that the port for Raspberry Pi is almost complete, and the build process isn't much more complicated than working with a BeagleBone. And while with the new BeagleBone Black there is no longer a significant savings in cost, success would help bring OpenROV into the ever-growing Raspberry Pi community.