Everyone knows linux is free, but it's not always that pretty. I stumbled upon this looking for a replacement os for a friend's xp laptop and I'm currently backing up my W7 installation to replace 7 with this - it's that good!
It looks more OS X than Windows, but the interface is minimal, it just gets out if the way. It's blazing fast installed (you can try the live cd/usb stick version first) and tweaked its functionality window and file-wise is easy to use from Windows users.
Screenshots? Image search 'elementary os'! Check out the video & YouTube reviews.
There's good community support, tutorials, and tweaks, and a dev team who value clean and meaningful changes, keeping it fast & sleak.
If you're looking for a change from Windows but don't have a mac or like the new Yosemite interface then take a look at elementary - I love it!http://elementaryos.org/