The Menu Customizer plugin was merged into WordPress trunk today and will be one of the headline features of the 4.3 release.
Roughly a week ago the feature plugin was tentatively approved for merge, pending an a11y audit and PHP and JS tests. Following an overwhelming amount of negative feedback from the community, core contributors published what was essentially a rallying call to get the plugin ready for merge, reaffirming their commitment to iterating with the customizer.
Nick Halsey, the plugin’s developer, published a number of UX flow and performance comparisons of the admin menus screen vs. menus in the customizer. Ryan Boren and Konstantin Obenland also published iPhone 5 and 6 emulations of the plugin in action.
Halsey’s overall conclusion was that managing menus in the customizer takes less time in most cases than managing menus in the admin:
For the tests, I added links to both Menus UIs to the admin bar (4.3 will have one link here, to the Customizer). I ran into a few areas where the experience could be improved, but in terms of timing, the Customizer version wins in most of these scenarios currently. Note that this is intended to compare the experience for power users.
The Menu Customizer is one of the most controversial new features added to core in WordPress’ recent history. It will be interesting to see how it plays out when users discover it in 4.3. Those who were not in favor of the feature voiced their opposition in comments on the original proposal and in independent blogs around the web but were ultimately overruled.
— David Decker (@deckerweb) June 16, 2015
At this juncture, no official timeline has been set for removing the menus screen in the WordPress admin. The existing menus will continue to be maintained for the time being, which should provide an easier transition for users who are surprised by the new feature in 4.3.