Overall stats are not that useful or valuable. Spotting form and out of form pitchers is the key to beating the number.
As for predictive value, very few power ratings will ever be of much use. They might beat the number 52 or 53% of the time, but not much more. You can't handicap games purely on one number, as much as we would all love for that to happen.
How I use power ratings is more in line with determining what results were seen against what quality of opposition. I also use them to spot improvement or erosion of ability over periods of time, but never as a lazy tool to try to make a pick. I use Sagarin's numbers for this all the time because they are easily obtainable and always updated. I use the Predictor as the rating to consider.
