I'm running Yosemite now. The same feel you get from iOS 7 UI is prevalent in the OS. They flattened the window headers. They flattened the toolbar on the bottom. They flattened the status bar on top. It makes for more of a content-focused approach.

The translucency they speak of is in regards to the side menus in apps. In order to give a dynamic feel to the UI, they added some translucency like they have in some iOS 7 apps.