Filezilla ... supports SFTP, and stays where it's installed, without bleeding over into your registry. FTP, FTP-TLS, FTP-SSL, FTP-SSL/TLS, sFTP, and an easy interface with Drag and Drop.
It's very similar, in fact, to the good ol' days of Cute-FTP where it was simple and easy, before GlobalScape started their funky shenanigans. Plus, it's free.