I replaced the stock transmission fluid with the RP stuff back in February. I wouldn't say there is an incredible difference but the shifting is very smooth once it gets up to temperature. I still have that notchy feeling getting into 2nd gear when the car is cold.

 

I am in the process of choosing an alternative to the more than $100 a litre OE Castrol stuff (I hate being ripped off). I was going to buy Royal Purple Max Gear but then reread this thread. Another line with strong supporters, especially in racing, are Lucas Oil products. Has anyone had experience with their 75W-90 synthetic gear oil?