again I find the airflow design.. disappointing. Not sure if there is a similar array of fans at the other side, but either way, it looks like just a copy/paste job while there was opportunity to make something much more efficient by orienting the boards differently and creating windtunnels.
That said, I still want one

Although I am sure there are ways to improve it, I don't think the current design is insufficient, and should work reasonably well - the side-to-side instead of front-to-rear airflow is also a welcome development. Remember - there is still a "supercomputer" yet to come... I feel that they will pulling out all the stops on that one, making it the ultimate system.
And for what it's worth, due to recent comments by BFL, I believe that as postulated by some, this is indeed a custom run of programmable devices of some kind. A custom device doesn't *have* to be single-purpose, it is just a lot harder to design a reprogrammable device. But it can be done.