I have been using MP3Tag for a couple of years and I find it to be one of the most useful programs on my PC, so kudos to the dev team. Thank you for a great program. That said, I have found a couple of things missing.
when using the Action->Capitalize Each Word, MP3Tag does not capitalize the word behind a parenthesis, such as (dance Mix), it would be nice to have it capitalize it like (Dance Mix).
It would be nice to have an action that converted brackets  to parenthesis () and the other way around, I am partial to parenthesis, and get a lot of mp3s that use brackets and I am sure there are a lot of people who feel the opposite, this function would be a great time saver.
It would be nice to have track # and total tracks in separate fields, I frequently get files that have the track number, but not the total tracks, and it would be a time saver to just enter the total tracks rather than have to re-enter the information on each song.
If for some reason, my suggestions already exist and I have overlooked functionality that is already built in to the program, please let me know.
Thanks for a great tool in my never ending battle to organize my music collection.
The Case Conversion action permits you to specify characters that precede words. I don't see it in the documentation, but apparently only spaces are used by default.
You can easily create an action group using two Replace functions, or one Replace With Regular Expression to accomplish this. An action to replace specific characters wouldn't be very useful to many people. Most actions have a lot of flexibility in what they can do by allowing users to provide configurable parameters.
Create a field and place the total tracks in it. To make it easier to enter the same data for multiple files (most often one CD), add the field to the Tag Panel (on the left) rather than using the file view (columns).