It is being rolled out over time, not to all devices at once. When yours gets it, you'll get a notification.
My personal decision is that even though it's already downloaded to my device, I am not installing it until some time has transpired to see if it creates any new problems for other users. This is because I am not having any substantial problems now other than occasional sticky keys. Those who are already having serious problems will most likely install it to see if it helps.