Yup, no frills pwm isn't terribly complicated. Lets dub that the "bad boy" controller (compliment of the "bad boy" charger), though best reserved for the adventureous types
The openrevolt has logic in it to make it a current controller, with pi loops and a couple over-current protections, and a large body of testing behind it, plus a lot I'm overlooking, so it easier to drive and should be safer for the average joe, if I understand it correctly.
edit: lots of info on the wiki you should be able to see:
http://ecomodder.com/wiki/index.php/Open_ReVolt