Trading Networks gives you more robust features for document resubmission and tracking than the FF package. With TN, you can set up trading partners, track document submissions through the logging mechanism, resubmit failed documents, and track documents by trading partner. It also contains some special functionality for the handling of large files.
You may want to spend some time reviewing some of the Trading Networks documentation - specifically, the Analyzing Your Network and Building Your Network PDFs (these should be in the doc directory of your TNConsole installation).
The documents refer to trading partners as external businesses, but trading partners can be anything from external businesses to EAI applications to your own internal business units. For example, I implemented one system with Siebel CRM, an Oracle data store, and a custom web application defined as trading partners. You decide how best to define these for your environment.
As a general rule, I like to use TN for the monitoring and organization capabilities that it provides, but your own situation will really determine whether TN is useful to you or not.