I'm a big fan of Wages of Wins stats, though I'm not as confident as Dave Berri in their accuracy.
I think the absence of reliable defensive statistics leaves out a lot of important contributions. Also, the statistical "advantages" of players who are allowed to play within their limits and thus produce superior FG% and low turnovers overrates some of the great role players(Rodman, Fortson and Rondo for example). However, I still think it's a great counter stat that underrrates the overrated and values the production of guys like Pryzbilla.
In answer to Roy Hobbs' doubts about McCarty or Baby's rankings, this is one area where I'm on Berri's side. I believe that players can be net negatives for their team, and that playing a guy like McCarty for 8 years will simply increase his negative ranking. He would have done less harm if he played less. The same goes for Baby. Look at Baby's season last year: for most of the year he hovered around 40 FG% at a position where the league average is around 50%, yet he took a high volume of shots. His rebounding and shot-blocking were also well below average. It's not that he produced nothing, it's that he produced so little relative to his peers and despite this played big minutes and took a lot of shots.
Now we Celtics fans know that Baby played primarily because the threat of his shot spaced the floor, his girth allowed him to defend some centers and he was a smart guy who made few onerous mistakes while providing some exaggerated hustle. He was not able to execute this skillset at a consistent NBA-level however, in fact falling far short, and thus was a net negative. But Doc's only other alternatives in the same skillset were Mikki and Scal, who were arguably worse.