I had the same problem of syncing data from s3 to a local filesystem where the data *never* was before: The missing directories are simply not created on the fly.

To fix this insert the following in the require section:

require 'ftools'

And add File.makedirs() as follows:

def updateFrom(fromNode)
    if fromNode.respond_to?(:to_stream)
        fName = @path + '.s3syncTemp'
        File.makedirs(File.dirname(@path)) # This is the important part!

    [...]
end

Perhapes, this could make it to the next release, please?

Best regards, Jan