Thanks for making this plugin! After reading your article a while ago, I went and wrote this exact plugin but luckily found yours before I submitted it to the repository. No need for more than one of these.
I checked out the plugin and discovered one bug and a few ideas :)
You're styling the div#wp-content-media-buttons rather than a#content-add_media. That leads to ALL media buttons (like the Gravity forms icon) to show up in one weird integrated "button." See here: Weird button with Gravity Forms. If you change the element you're styling to the link instead, you'll also catch the Quick Press's "Insert Media" button which is currently unstyled. It's tempting to style ALL links in that row, but I'd shy away from that on the chance that other plugins style their own buttons.
- Style-wise, I wish the :hover and :active states more closely matched WordPress's defaults.
- To get really nit-picky, the WordPress admin button's have a border-radius of 11px.
- To make things a little more WordPress friendly, I'd use wp_enqueue_styles() hooked to the admin_enqueue_scripts hook to register the stylesheet.
So thanks again for making the plugin. If you incorporate these changes, I'll definitely be adding it to all my client sites.