I just noticed that all 10 binaries for MP3 Diags have finished building, so I guess it's time to announce that the first public version of MP3 Diags is available.
To quote the home page, MP3 Diags is a GUI-based application that allows end-users to identify issues with their MP3 files, fix some of the issues and make other changes, like adding track information. It also lets you "look inside" an MP3 file.
It looks at both the audio part (VBR info, quality, normalization) and the tags containing track information (ID3.)
MP3 Diags has a tag editor, which can download album information (including cover art) from MusicBrainz and Discogs, as well as paste data from the clipboard. Track information can also be extracted from a file's name.
Another component is the file renamer, which can rename files based on the fields in their ID3V2 tag (artist, track number, album, genre, ...)
For download information and documentation see the home page at: http://web.clicknet.ro/mciobanu/mp3diags/index.html.