serverside (3.0.x):

unix charset = utf8
server string = ようこそ
#(the "dos charset" should not matter in this case)

...

when you do on a samba 3 smbclient (also running in UTF-8 locale) 

  smbclient -L servername

... you get

Password: 

        Sharename      Type      Comment
        ---------      ----      -------
        c$             Disk      Viren-Falle
        programme      Disk      
        IPC$           IPC       IPC Service (ÒéêÒüåÒüôÒüØ)
        ADMIN$         IPC       IPC Service (ÒéêÒüåÒüôÒüØ)

        Server               Comment
        ---------            -------
        JSTEWART             jstewart
        LUX                  ¤Ç╬▒¤üߢÀ¤â¤ä╬▒¤ä╬▒ߢÀ
        LUXILEIN             ¤Ç╬▒¤üߢÀ¤â¤ä╬▒¤ä╬▒ߢÀ
...