There were lots of oohs and aahs in response to Apple's software engineering chief Craig Federighi showing off a new dark UI mode in OS X Yosemite at WWDC two weeks ago. It basically alters the appearance of the menus, sliders, buttons, windows and other UI elements.
The gorgeously subdued look is inspired by the dark appearance of Apple's pro software such as Aperture and Final Cut Pro. In fact, I like it so much that I enthusiastically tweeted right after the keynote that I was very much looking forward to using it on a permanent basis come this Fall.
However, dark mode was notably absent from the first beta of OS X 10.10 and is nowhere to be found in the just-released Beta 2. For a good reason, too, as it's unfinished and very much work in progress so not really ready for prime time yet.
If you're a type of person who can't wait to see it in action, you can enable Yosemite's dark UI using just a simple Terminal command...