re: Poker & Poker Tracker
Poker Tracker has many options, and different people use it in different ways.
I personally find it most useful for post-game analysis of my own play, but many users rely on it for in-game study of opponents. You can use either method or both, according to taste.
If you succeed in plugging leaks in your game, this will of course carry over into live play. Opponent analysis is, as you say, useful only in the here and now.