I've never thought of it to that detail before. I knew from experience it felt like adding rear wheel steering when I increased toe out so I guess that makes sense now.
My alignment guy races spec miata's and he was telling me to increase the rear sway bar instead of adding toe out but I've always felt I have enough or maybe even too much stiffness in the rear sway bar (not enough rear suspension indpendence). I increased the rear spring rate to 8kg/cm (same as the front) and I couldn't tell much difference at all. I increased the rear toe out to 1/4" and the car handles so much better. More throttle off oversteer and the rear end really feels like it has rear wheel steering. After I increased the rear toe out I was running too tight at the exit of the turns because i wasn't used to the car's front end tucking in instead of pushing. Its a significant difference.
I don't think rear toe out would be good for high speed driving but its great for autocross. Its an easy way to fine tune the handling of the car after you get everything else set like you want it.
To answer the original question... my times are faster since I've gone from 1/8" rear toe out to 1/4" rear toe out. The car is a little twitchier but its much more neutral (less understeer to no understeer) in most situations.