Even before taking over officially he was the de-facto GM. There was some ugliness early on but there isn't much to argue with over the past few years - Got Camby and Rasual Butler for 2nd rounders, signed Baron, drafted Blake, Gordon, and Jordan. The ZBo experiment didn't work out too well but he was able to unload that contract and turn it into Rhino and Telfair who have been good role players.
He did botch the Elton Brand thing but that turned out to be a major win seeing as how he sucks now.