I have the sport, touring, Nav and the sports package is essentially free considering the value of what you get.
The touring is for comfort and figured I'd never end up on a track, being as old as I am, I'd like the creature comforts. And I do, but I am at the track and would like to dump the 100 lbs at the track but only then.
The Nav was considered useless the day I bought it but I have learned to like it quite a bit. The music box feature being my 6 CD replacement.
I bought my Z brand new with 7 cars to choose from. With 2011 looming the 2009 had to go and I paid $32,900 fully loaded vs $40,000 plus.