First of all, thanks for sharing this great plugin.
However, I have little problem with the display of taxonomy terms in "Add media" window sidebar.
When used with default "Category" taxonomy it works perfectly fine. However I needed a custom taxonomy, so I registered one and used your mc_filter_taxonomy function to replace default taxonomy with a new one.
Now the plugin displays correct taxonomy but in a distorted way. You can see the result in this screenshot.
I'm just curious if it's a known problem and if it can be fixed with some kind of quick CSS tweak.