It's been out for ages and I'm pretty sure Windows 8 has it as standard now but if not you can get it through Windows Updates I think. :good:
It's handy but I still have my NEF files (Nikon RAW files) opening up with Lightroom on my machines because that's what I use to process them. But on other people's machines it's cool because they can view my NEFs without needing software to process them.
I've had it for a while now as well. The only thing is I shoot with two cameras. A Sony a33 and a230 both produce .ARW raw files. Though only the raw files from the a33 are viewable. I have no idea whats up with that.