All he's doing is using the iMac as a display I don't understand what you are asking ?
What I'm looking forward too is Thunderbolt External GPU's that should be a very interesting and great way to get enhanced performance on such machines that cannot be upgraded.
Imagine having a super ultra thing laptop like a macbook air... with a "get by" gnu inside thats good enough for HD video etc and maybe some light gaming.. then when you want to do some heavy gaming you just plug it into your thunderbolt GPU on your desk and game away.
Fantastic