I'm not sure where the line between TRAMP and Ange-FTP is, so maybe I need to report this elsewhere - if so, please let me know.
I'm having a problem with using mkdir or make-directory on an FTP host when the directory already exists. If you give t for the parents parameter to mkdir, it should silently ignore it when the directory already exists. This works for local directories as well as remote ones using ssh/sftp. However, using ftp, it throws an error when the directory exists.