I have one on my car. More due to the uniqueness of it, but it's visually repetitive. I had read that someone had a noticeable difference, but it gets subjective pretty quickly with this kind of stuff. I also have the DoLuck RXB which I've read mixed reviews about. No first hand experience yet since I've been too busy to finish my car anyway.
I would like to think companies like JIC and DoLuck did their fair share of R&D with our cars (expecially with targa cars) back in the day to warrant using the pieces they produced.
Kevin