I'd say use it sparingly and you'll be fine, I've played with it on and off, and it does give you some extra "oomph", but transmission longevity is a concern.

 

I have been pulling it back into I for over 80K it still shifts fine. I had to replace the TCM for no speedo and door locks unlocking and locking when driving. Because it was pulling down the data line to BCM. But nothing with trans. it self.

 

Unless you are pounding on the gass and shifting to where the RPS are solid high, I wouldn't think the normal "pass an A*$" or using it to chugg up a hill would hurt it at all. Wouldn't hurt it anymore than having the shift points changed by a tune. Now....if you beat on your Trans, it's bound to pop somthing anyways. I know the Transmissions aren't bullit proof but with most of us, it'll last while driving happily through our lives using "I" a few times.....

 

I Love I in the SS. Holds gears forever, nice cackle from the exhaust on downshifts.