GuildFTPd being the most popular FTP server for windows, is also the most customizable. You can add as many users as you want, and change anything the user can do.
GuildFTPd also features system event messages, sound events, spy features, upload\download count, speed limiters, hammer banning, ban on noop, resume upload\download, and more. This is just a small list of things GuildFTPd can do. Check it out!