I tried the Taxonomy Multi Editor during one attempt to get Drupal's taxonomy working but pulled Taxonomy Multi Editor out because it just made diagnosing problems harder. When you install Drupal's taxonomy related modules, install them one at a time and test each change. You need to be clear about the effect of each module.
Some modules add extra fields to the page editing forms and some of the extra fields lack distinctive identification. You end up with a mess of fields that overlap in function. I removed a bunch of taxonomy modules, including Taxonomy Multi Editor, and then went back to adding the modules one at a time. In one case I changed some identification text to say which module added the field.
You can use Taxonomy Multi Editor when you have single pages appearing in several vocabularies. You might have one page on grapes added in to a vocabulary on gardening, a vocabulary on food, and a vocabulary on wine. If you have lots of vocabularies and rarely add a page to more than one vocabulary, the Taxonomy Multi Editor module just makes your page editing form too long and complicated.
Download Taxonomy Multi Editor from drupal.org/project/taxonomy_multi_edit.