The REV3 board is built and working great. No issues discovered so far.  This rev features improved performance, a few fixes, and a two-way IORQ line so that the AVR can control peripherals such as the RomWBW paging registers, or my new TMS9918A board directly.  I've detailed the changes in a previous project log, so I won't rehash them here. Instead I'll just share some pictures of the completed REV3 board.  If you want to make your own REV3 board, you can have it manufactured using the gerbers attached to this project, or from the shared design on OSH Park.