Brandon LeBlanc at the Windows Team Blog:

Today, I am excited to announce that Windows 8 has been released to manufacturing (RTM)! This means we’ve completed the product development and testing of the product and have started handing off the final code to our OEM partners. They can now begin preparing new Windows 8 PCs and devices they’ll introduce starting with General Availability. For more on RTM, I suggest reading this blog post from Steven Sinofsky on the Building Windows 8 blog.
We're now step closer to the final public release and likely only a few months away from the Surface tablet.