Hrm, got Rev 3 it seems:
Did you put that hole in the side for the PSU fan ? Or is that a late batch 2 case ? My B2 does not have that case..
Interesting. I am curious as well. This is how they should have been designed. All of my cases are closed and the PSU turned inside, thus blowing the hot air inside the unit.
That's an intake fan, not exhaust.