Some good reading:
Forced Induction & 7AT 370z Info
On the note of Stillen failure, I would not say the "parts" fail but people have had more issues with Stillen. I have seen many Stillen SC kits installed without problems, just have a good reliable installer and a good tune (do not use the Stillen tune). The main thing with the 7AT is the TQ, stay out of the upper gears when in boost, with doing that, a good cooler and transmission adjustments via the tune it can be ok.