i think people have been taking this a little literally, I mean obviously this was never going to be a 100% efficient system, as that'd break the laws of thermodynamics!
But think of it this way, heat is a form of energy, while it is of course difficult to convert back to something useful. But if you were able to regain 10-20% of what you are outputting in heat, it's still something! This will be difficult of course, but if you were able to make a PC 5% more efficient over all, then that is something, yes?