Maybe it is just the hype, but right now it is night and I don't feel like there is as much strain on my eyes. Usually I would be looking at a very bright screen.
I work off my laptop and desktop mainly. I only installed this on my desktop and it definitely feels like there is a difference.
These people should leave it as free for desktops and make an app for cell phones and ipods. For 99 cents many people would consider it a great buy.