The only mods I regret are:
-Shutting the garage on the roof the night I bought it and getting some scratches
-Leaving the tailgate up while in the garage, then walking out the side door only to come back and try to open the garage door over, and over, and over again until I realized the tailgate was actually stopping it...more scratches
-removing the rear silencers (it sounds pretty good actually, but RR's aren't supposed to sound like chevys)
-Toyota FJ Cruiser shocks (immediately removed them and installed Doetsch Techs)
-Bypassing the lower seat heater elements (they were broken) to get heated upper seats...only to have my wife fry the passenger side and ruin the leather
Best mod.... Rockford Fosgate 6.5" subs in the stock box with a cheap Alpine amp. Makes my Beastie Boys and Rage Against the Machine sound nice.