Cliff Seal

Simply put: this plugin gives the Editor role access to edit “theme options”, which includes:
<ul>
<li>Appearance > Widgets</li>
<li>Appearance > Menus</li>
<li>Appearance > Customize if they are supported by the current theme</li>
<li>Appearance > Background</li>
<li>Appearance > Header</li>
</ul>
Instead of adding this capability by hand on each client site, just install and activate this plugin—it keeps your <code>functions.php</code> file clean, and keeps this type of functionality where it belongs.
The capability is added to the role once (on plugin activation) and removed when the plugin is deactivated.

Editor Theme Options

Allow editors to access theme options in the Appearance menu.

sevenspark

The new accessibility javascript in the Appearance > Menus panel in WordPress 3.6 can significantly slow the page load speed when using a large number of menu items (> 50). This plugin defers the accessibility processing to eliminate the scripting bottleneck and allow the Appearance > Menus screen to run much faster and more responsively.
<a href="http://sevenspark.com/wordpress/speeding-up-the-appearance-menus-screen-in-wordpress-3-6" rel="nofollow ugc">Full details</a>
This solution is fairly rough. Hopefully we can develop a robust solution that can eventually become part of the core. Pull requests through GitHub are welcome.

Editor Theme Options vs Faster Appearance – Menus