Marc Bizer (and others) wrote to address Matt Neuburg's complaint in "The Postman Rings Again" in TidBITS 424. As with almost everything else in the consummately flexible Eudora, you can revert to the old look that featured letters instead of icons in the status column of mailboxes. To return to the previous look, enter this one-line AppleScript into the Script Editor and run it (it will ask you to find Eudora Pro). The script changes your Eudora Settings file; to reverse its action, rewrite the script to set setting 233 to "n" and run it again.
tell application "Eudora" to set setting 233 to "y"