I have released version 1.51, which includes support for the enhanced category/tag selection metaboxes in the ATTACHMENT DETAILS pane on the right-hand side of the Media Manager Modal Window.
To activate the new feature, install and activate this related plugin:
Media Categories, by Eddie Moya
Then, open the Settings/Media Library Assistant screen, General tab, and scroll down to the Media Manager Enhancements section. Check the box next to Media Manager Searchable Categories metaboxes and/or Media Manager Searchable Tags metaboxes, depending on your needs. Click Save Changes to record your choice.
I intend to add something like this as an MLA feature in a future release, but this interim step is an easy change that should give you some of what you need. The only drawback to the "Searchable" metaboxes is that you can't type in a new category or tag value; you must pick from values already defined on your site.
Please let me know if you have any trouble with this new feature, further questions or suggestions. Thanks for your interest in the plugin and for this suggestion.