MP3-Info CMM has been updated to include support for AAC files.
That is essentially an extension to the Finder.
It displays information about MP3 files, such as their duration, the bitrate, and also some important MP3-Tags, such as the artist, the title of the song, and some more, all directly inside the Finder, without the need to open any application to get this information! That can save you a lot of time when have to manage MP3 files often.
It also shows these information for AAC files created by iTunes 4, and WAV, and AIFF files.”