Sorry, but I have no personal experience with the Iridium. I just run straight tinted windows on my Arai.
I do, however, have a 6yr old pair of Oakley shades with Iridium lens that have yet to get major scratches on them. And we all know the average lifespan of sunglasses.
I also ride with a guy that has the blue iridium aria lens. He loves it. He almost had me talked into it. He claims they don't just make things darker, but they change the tint and glare. So, he can use it at night.