He made Steel a cool and functionable member of the JLA. He's the only writer who's actually written Kyle Rayner well (imho). And he brought Plastic Man in (finally!). WW3 was, as Chewy stated, the culmination of everything he began when he started his run.
If he had one real problem during his run, it would be too many recurring plot devices, such as villains breaking into the Watchtower, the JLA almost being fully defeated, Batman saves everyone at the end, etc. His overuse of many of these devices, keeps WW3 from being as powerful to many of us as it should be. My own personal opinion being that Rock of Ages is his best JLA work, but that's another thread.
