1) You can now merge tags. When you rename a tag to another tag name which already exists, it will combine those two tags into a single tag using the name you specify.
2) You can select up to 10 of your tags and enter new tag names to add to all entries which use one or more of those selected tags.
If you run into any issues using this new page, please comment to this entry in lj_releases to let us know. Thanks!