VB Upgrade was in my top 5 best mods for my 350Z. I went with it cuz I run spray. It almost behaves like a manual and at WOT it slams down into gear almost feels like damaging something but you are not. off spray it would chirp the tires 1-2, 2-3..so worth the $550 (250parts/300labor). Heat is the killer of ATs. Go with a B&M Hi-Tech tranny cooler with the integrated SPAL fan. I placed mine on the under hatch-trunk heatshield between the HKS dual canisters. I avg 180d fluid on hot days, but using tiptronic will increase fluid temps closer to 195-200 from what I have experienced. The hotter the constant running fluid temp the less life you get out of the juice requiring more frequent changes. Generally these coolers daisy chain onto your radiator requiring good airflow against it, and I would not bypass your radiator unless the cooler has an independent T-stat switch and cooling fan.
I would think this mod is a MUST for any FI application.