I have used multilaunchbox on to box on 2 different macs after 4.0.3a for the same reasons you stated. It worked as advertised for me. I got frustrated not being able to use the mouse on the second computer and went back to a synergy broadcast / clonekeys solution. I am not too happy with that either (the synergy part) I am planing on upgrading my mac pro to try and get everything back on one computer.