To me the key point of Moneyball was not was not any of the individual stats but rather the use of the stats to look for things that are undervalued in the marketplace - essentially applying the concept of arbitrage to baseball.
For example, at the time of Moneyball's writing (e.g. before publication) the A's were focused on the notion that On Base Percentage was undervalued by the baseball teams in general and that by focusing on getting players with high OBP you could get better value than by focusing on players with high slugging percentages.
Since Moneyball's publication, MLB teams (along with the media) are now all talking about OBP and, I would assume, the value is no longer there - players are now properly priced for OBP.
The interesting question to me is have teams moved on in search of other stats that reveal undervalued players where you can get a "cheap" player who is worth more to the team than his price. I am really encouraged to see Billy Beane backing up the bus and reloading his team - and am curious to try and figure out what is his new key stat. I am thinking, based upon hints dropped in various articles, that he is now focusing on defensive stats - an area that is still a largely unexplored area of Sabermetrics.