Software Summary:

Full Tilt offers one of the best software packages online.
Its easy to use, does not slow down, looks clean, and has many useful and innovative features, such as a button you can use during tournament play to determine your current standings with a single mouse click.  Some players feel the avatars are a bit cartoonish, others love it.  (In any case the avatars can be turned off for those who want a more utilitarian playing experience.) The overall feeling is an easy to use, good looking, and reliable application.

More Features:

Full Tilt does a good job with its statistics tools.  You can take notes on other players who you play against by right clicking on their avatar.  The Lobby view also displays some critical information about in-room play such as flop %
called, and hands played per hour.  A nice added feature
on Full Tilt is the ability to see notes that you've taken
in the past from the Lobby view.  That way you can better know weather or not the room is one that you'd
want to play in or one you'd rather avoid.

Other special features include a tool to automatically refill your chips at cash games when you fall below a specified amount-this way there are no distractions from play or getting automatically sat-out in case you go bust.  There is also an option to take satellite winnings in credits rather
than having to play a specific tournament.  The more standard features are included of course, such as the time bank which allows added time for tough decisions, and a
log-in history.  And yes, Full Tilt is compatible with Poker Tracker.