Apple changed the behaviour of the small green button in the window controls from “Maximize” to “Fullscreen”.
I used Maximize all the time, and now found how to get the behaviour again. You
need to can double click the title bar (or combined toolbar, e.g. in Safari) to get the old “Maximize” behaviour. No idea if that was like this in Mavericks and before as well already…
Update 07 May 2017:
Or you press the
Alt (⌥) button and then click the little green blob, like everyone else.