I don't think we can control hashrate but the dev selected a PID algorithm (http://en.wikipedia.org/wiki/PID_controller) to control the difficulty and it seems to be working as designed. I studied control systems theory in college and i'm intrigued by how this could be applied to control difficulty on a cryptocoin.

Remember from the OP, setpoint is a block every 180 seconds (or 100 blocks every 5 hrs). As far as I can tell the PID is right on getting there.