I have a TCI Stage 2 shift kit in my transmission and I have nothing but good things to say about it. Shifts hard, very accurate and has been that way for the passed 5 years. The only thing is that you can't downshift while in motion, only once you're come to a complete stop.
A Stage 3 shift kit will allow you to up shift & down shift, but there is no automatic mode... meaning you have to do all the shifting all the time.