Is it merged in today's build? It seems not to be available in the 28.0a1 (2013-11-18) OS X build/update.
edit: a new update is now available with the new changes, I _like_ it!
edit': a minor quibble though, I preferred the star button when it was directly integrated in the url bar. I find it too excentred from the url for my eyes, I often give a quick look to check if an url is already starred or not.