Poker Tracker hasn't been updated in years, so has a clunky interface, and is slower than molasses. (An update is apparently in the works, though).
I've started using Holdem Manager (see the lengthy thread in the Software forum, or go to
www.holdemmanager.net). It's several times faster, much prettier, has customized stats, customized reports, graphs, tracks rakeback & bonuses, etc. Overall, it's a much better piece of software than the current incarnation of PokerTracker, with features PT users have been asking for for years. It does not currently had a HUD, but one is coming real soon.
Cheers, Carl.