Since the advent of the Major League package I have seen virtually every Red Sox game since 2003. I have read James's book and a few others as well. I've learned far more about Sox players by watching them play than by reading their stats, all their stats including the so called advanced statistics, The so called advanced statistics aren't really that advanced they are just a different way of describing what HAPPENED. I agree that the new models are great for comparing past performances of different players. However, as we have seen over and over again with Bill James projections they simply have their drawbacks. Otherwise we would have celebrated more World Series titles then we have had. Marveled at that great Red Sox Short stop Renteria; WMB would be starting at third, we would be toasting that great aging Red Sox outfielder Carl Crawford, you get my point
I've learned nothing beats watching guys play every day. Bradley Jr is one example, after seeing him play one sees his flaws which weren't reflected in his earlier minor league stats.
Whenever you buy stocks or equities, your broker always reminds you that "past performances are no guarantee of future results" so to with Sabermetrics. Enjoy them for what they are. As for me give me a great scouting dept full of guys who played and taught the game. They aren't perfect either but they bring perspective which is often lacking in pure quantitative analysis.