And I thought wiring was going to be the difficult part. Wiring was a breeze compared to button configuration and troubleshooting (phew!)
Finally managed to get everything up and running, and it was a blast. Played some track and field, street fighter, TMNT, and some rampart to test out the 3 trackballs.
Unfortunately it looks like the x spindle on one of the trackballs is messed because it doesn't spin very freely unless heavy pressure is applied to the ball. Whee, have to get that RMA'd.