I think the jury on Towles should still be out.
You could also go another year or so back and add Hirsh, Talbot and Zobrist to that list. The Astros have done a pretty good job of evaluating their guys in the minors, maybe not when they drafted them, but years later.
I don't miss Cusick, but the move does seem kind of pointless. Isn't there someone at Round Rock who could give you a 5+ ERA out of the pen, for a much cheaper price?