It was there for me, just a prompt at the top with a short message and a green button. A quick reload later and there it is. Staggered roll out I suppose.
I just got a notification/alert at the top of the site saying something to the effect of "would you like to try out our new layout?" yes please. voila.
I guess they are slowly letting users opt in. Seems incredibly weird and slow considering the public featured announcement on the blog.
It says over the course of the next two weeks, you'll be able to opt-in so its being slowly rolled out.
Don't see it either. Maybe badly worded.
@mdo said they're slowly rolling it out, and when it's available then you'll be prompted on the repo you own.
That's an interesting choice of rollout if you enable it for all users that see your repository instead of enabling the view for yourself for all repositories that you browse.
I would imagine that it is easier on Githubs end to configure a repo to render one way or another rather than to conditionally render it based on the current user.