WordPress 4.5 is right around the corner. Release candidate is now available for download and the final release will be available on April 12. Among the changes a bunch of new features with the customizer. I particularly like the three below.
1. Site responsiveness can be previewed within the Customizer
Improvement description can be found here.
2. Selective refresh in Customizer
Full description is here. Selective refresh will allow for super fast changes without having to reload the entire preview. YouTube demo is here. All of the default WordPress themes and core widgets will ship with selective refresh in 4.5, but the feature is opt-in for plugins and themes.
3. Custom Logo
Full description here. Custom logos utilizes the Customizer’s brand new Selective Refresh feature. The latest two default themes will be updated with support for this brand new feature as soon as WordPress 4.5 ships. Themes that have been using Jetpack’s Site Logo implementation will not need to be updated—Jetpack will do a migration behind the scenes to work with it out of the box.