I leave it totally open ended… Whether you’ve used them or know something cool about them… fire away!!!!(I though it would be interesting to start something like this, especially to help beginner learn and more advanced users to recap on some of the wonderful features of SharePoint that would otherwise not get the attention).
To answer my own question – all the documents in document set are in the one library – a document set is really a fancy folder, so itself sits in a document library.
Can’t seem to find an obvious way to move an existing item into a document set using the GUI – unless its so utterly obvious I’m overlooking it?