Under Windows I had to change the following

In the s3config.rb file update it so it looks in the local folder (where s3sync.rb) is for the config file.
  confpath = ["#{ENV['S3CONF']}", "#{ENV['HOME']}/.s3conf", "/etc/s3conf"]
to
  confpath = ["./", "#{ENV['S3CONF']}", "#{ENV['HOME']}/.s3conf", "/etc/s3conf"]

I didn't want to mess with the environment variables.