Jason Snell writes about some of the inconsistencies in Mac OS X 10.10 Yosemite, such as how only a few of Apple’s own apps use the new combined title bar / toolbar style:
"It makes me wonder if Apple was initially enthusiastic about this approach, then realized it wasn’t applicable to many situations, and rather than abandoning it just decided to live with the inconsistency. There’s certainly no clear, this-is-the-future signal."
I don’t hate the new style, but that does seem like the fundamental problem with it: it can’t possibly be used for all apps, especially those with lots of toolbar buttons. I considered it for the next version of Clipstart, but it’s not really a compelling enough change to risk breaking things that already work well.