I use foobar for most of my tagging needs, but MP3TAG is invaluable for cleaning any extra 'invisible' garbage out of files.
One major problem I have is:
I have a file/album that includes the RELEASETIME tag in foobar.
I open that file/album in MP3TAG, select Extended Tags..., make no changes and select OK, so the files resave.
Now the RELEASETIME tag is remapped to RELEASE DATE.
I've also tried setting the mapping options in MP3TAG : ID3v2 > RELEASE DATE > RELEASETIME, but that does nothing.
Any help appreciated...