Level 10
Mozilla has released the Quantum version of Firefox numbered as 57, via release channel.

You can download desired version (win32-win64) and install directly via here. No uninstall of previous version or anything required. Close the Firefox and run the setup and voila, your brand new engine Quantum is at your hands! :)

I have already installed it and can confirm it is simply magnificent! For those who do not want to deal with running a setup, you can still wait tomorrow for an auto-update.

Enjoy! :)