I have a fan (120mm Panaflo @ 7 volts) sucking air into the case and a vent in the back for the air to exit. The heat in the case is probably coming from the drives.
When I first got it, I thought this little YY cube was going to be a good case, but it really is still too cramped for what I have in it (I don't get the impression that there's good side-to-side ventilation). I'll be posting pics tonight I hope.
I'm currently lusting after the MountainMods UFO case (
http://www.mountainmods.com) - 18 inches of cubic goodness.