I use PokerTracker and like it fine. I probably don't use it enough, really, but mostly to track my wins/losses and earning rate.
If you are taking a break from actually playing I think a better investment than PT would be either Small Stake's Hold'em (if you're going to play limit) or the Harrington on Hold'em books, if you're going to play NL or NL tournies.
SS1 isn't going to cut it at online small stakes games, and I haven't heard of the other one.
Buy one or the others or both, become a winning player then go back to
PSO and get PokerTracker for free.
Mike