I loved Poker Tracker three. It worked great for like the first three months. Then with the updates, it's having huge problems with bugs. I suggest Hldem manager. I have that now, and it runs way a lot smoother. Holdem manager, is cheaper to purchase than Poker Tracker three, and a far better program.
A tracking software is worth it at the lower levels, you just use it in a different way. Don't rely on the stats, make good poker decisions and let the information the software gives you help you make decisions. I know it took me awhile to learn that.