The best use for PT, IMO, is for table selection. You can't tell too much about most opponents from a couple of dozen hands, but it is pretty easy to spot players at the extremes. For example, a guy limping 7 out of 10 hands and never raising is an easy target. You can also spot the nits and the maniacs after a couple of dozen hands.

The biggest leak that most players have, IMO, is sitting at lukewarm or worse tables. The opportunity cost is pretty big when you consider that you are trading blinds with a bunch of TAg's while there is a maniac on the next table trying to give his money away.