This isn't for doing a full sync or anything complicated -- for that you want something more like Interarchy or Transmit. It's not even for downloading; hence the name "OneWay." Instead, it's for fast and painless uploads.
There's only one feature that I would really like to see added: the ability to copy a public URL for a file after uploading it to a web server. I suggested this to the author, who agreed and said to look for that feature in a future update.
OneWay requires 10.5 or above. Source code is available on GitHub, and you can find the download link at the Source URL below.