If you are tired of paying for FTP client like CuteFTP or WS_FTP Professional, but haven't been able to find a good replacement, well, you obviously haven't found FileZilla. It's free, it's open source and it's great.
FileZilla is built on wxWidgets, which is my preferable choice for C++ Cross-platform toolkit, allowing it to be compiled on many operating systems. Ready made binaries are available for almost all the major platforms. On Windows, install is very easy, but this may vary on different platforms.
User interface is pretty intuitive. You can traverse the server and your computer without any problems, with mouse and keyboard as well. Site manager manages you FTP, FTPS, SFTP connections with ease.