We've been using PD for going on 7 years.  ... We were merrily dealing with our prospects and customers when I suddenly realised that PD could handle our supply chain as well. .... (well, given our specific circumstance). 

We work with a large e-commerce store and often order samples be sent from our suppliers directly to our customers.  ... We often drop-ship the eventual orders (that is, have our supplier's warehouse ship directly to our customers). 

It took a little time but we entered all our supplier orgs, and associated with those supplier orgs all the relevant contacts AND created contact records for all the functional email addresses  .. such as supplier newsletters as well as supplier invoice addresses, no-reply addresses etc.  

PD syncs across our mail and automatically associates it with our suppliers.  We can take correspondence from a supplier about a specific customer order AND associate that email with the customer deal (it is already associated with the supplier org when mail items are synced into PD)

It's powerful stuff but particularly useful when reading through a customer deal and being able to see all customer AND supplier correspondence.  ... a tad more work associating more mail to deals. .. but worthwhile. 

It's also nice to be able to look up a supplier and see all the correspondence in one place.  .. see their contact lists (including all functional addresses you have entered).  You can lookup a supplier and reading through the associated mail, see all the associated customer deals. 

Anywho.....   It took us 2 years to have this supply chain epiphany ...   doh!  

I hope someone here in oz finds this useful.