I finished building the MegaSquirt ECU last night. I went with a V2.2 board for MS1. The other box its connected to is the MS relay board which is a great convenience. I chose to use a relay board instead of the stimulator to test and that worked fine. The assembly was very well organized and the board tested fine at the end so I can't wait to get it in the car and turn the key.

Here it is in its finished state:

The bottom of the board houses a fet driver, voltage reg and the MAP sensor:

And a few hours earlier without the input or output sections completed: