Hmm. Not working for me in WP3.5. After upgrading to the 3.1 version of Media Tags, the "Show Common & Uncommon Media Tags" links are just totally gone.
When clicking 'Insert Media" from the Post editor, there used to be a field where you could type in your Media Tags, or click on the links to see Common or Uncommon Media Tags, without having to leave the dialog for uploading files. Now it seems that all is left is just a Media Tags link on the left of the gallery panel of images, which shows you a list of Media Tags nicely enough, but that's not very useful.
Interestingly, in this situation, seeing the list of Media tags, when you click on the number link (showing you the number of items that have a particular Media Tag), then you do get a chance to change Media Tags for items, but it's not as intuitive as before.
I feel like there should maybe be a little panel to the right of the image, but there is precious little room. Ideally it should sorta be like it used to be, or something like this:
There is probably some other way to control the Media Manager, maybe by loading a special panel or something that would show the list of images attached to the post, and let you edit the Media Tags there. I am thinking
might have the right direction, as it shows you how to make a custom "Set Default Gallery" modal box.