HTTP is just as reliable and fast as FTP. More reliable since there is only one connection instead of the separate data connection with FTP so less firewall worries. And you don't have to worry about a separate server with different authentication.

Also, if you don't need other form fields (including the filename), then you can do a POST with the file content as the body. The receiving CGI would not use CGI.pm to parse the upload but read the body directly and save it to disk. The filename would have to be constructed by some other mechanism.