Blackbird's suggestion works for me. But neither Dolphin nor Konqueror in KDE4 give any more than the basic file information.
I download a lot of podcasts of radio programs, and, in KDE3, hovering gets me a description of the programme content* as well as the file info. This is useful when I have a stack of programmes with the same title but with different contents.
* In Kde3 I get the mp3 details too: Artist, Title, Album, Genre, Year and Comment.