That kit makes a nice difference. I don't care what it did for my ET's, but I know I love the way it shifts now. The install wasn't too bad, my buddy did most of the work. I installed the cooler and he did the rest. Time-wise expect to spend at least 3-4 hours to do the job right.
I had them do the 2nd setting and couldn't be happier. I have 10,000 miles and going strong. I would guess mabye a tenth difference, two at the max. Compare granny shifting to powershifting. I rip 2nd and chirp 3rd now. If you want more info check out the search page, just look up trans-go. There are four or five good threads with alot of info for you.
A few guys have posted about how the TransGo ruined their trannies. Thats a very small percentage, and there's no proof that's what caused the breakage.
Then there is Jerry W., who designed the 40R70W, he says that the TransGo is terrible, but didn't quite explain how it could ruin a tranny. The shop I went to does ALOT of TransGo installs, he says he has never seen a problem from a TransGo.