I really like the program Mp3tag and I since I know that my favorite things (Winamp and Audioscrobbler) support ID3v2.4 I use this tag-field.
It is much better than ID3v2.3 but I have one plea:
Please add the MUSICIANCREDITLIST-field (it's the TMCL field) and the RELEASETIME (TDRL)-field. The first would help to differ people that helped to make the record and those who really were the musicians. And the second field would be helpful because in ID3v2.4 you cannot use DATE anymore.
It would make me really happy as those two fields are really helpful.