As an Mp3tag user under Windows and also under Wine/Linux I'm over the moon to have discovered such a powerful, feature-rich and intuitive alternative in Linux. It offers just about everything Mp3tag does (actually I can't think of anything it's missing) and includes a host of additional features such as tag source track-level tagging, automated tagging of an entire directory tree using one/many tag sources (musicbrainz, amazon, freedb and discogs support is built-in), an intuitive interface for accepting/ rejecting changes, ability to add/amend tag data before writing changes from tag sources, incremental tagging whereby existing tag data is preserved and only new data is added, ability to map tag sources to tag names of your choosing, ability to assign keyboard shortcuts to actions and ability to copy tags in a 1:1/many fashion. It also has a feature rich function and scripting library that enables you to automate almost any tagging activity. I'd never have believed it, but puddletag has taken Mp3tag as its baseline, and then lifted the bar enormously.
I'm blown away!