Ahh, here we go. General consensus seems to be that the most important additional channels in 10.2 are the "high left" and "high right", which provide most of the spaciousness and allow the listener to compute the size of the original venue.
There seem to be 14 channels in 10.2, not 12. Apparently the 10.2 moniker is meant to indicate that it is "twice as good as 5.1", even though the format is actually 12.2 not 10.2. Go figure.
Interestingly enough, nearly all of the added channels are intended to "convey the sense of spaciousness which can not be properly reproduced in 2.0 or 5.1".
In other words, if you are going to build a dead listening room you probably want to think about pre-wiring for those extra channels right now
