I'm in agreement - I did the swap on my ED6. The linkages are the same and everything, it was very simple.
The end result ? Not much more. the 4th gear in the 4 spd is higher than 1:1, so you'll get a couple more mph for the rpm, but it won't change your life.
Now adays, I prefer the gearing of the 4 speeds - especially for autocross.