Not sure these count as "lesser-known abilities", but these are a few of the places where I use Interfaces outside machine automation:
Interface Itemducts with the ME network:
Here I am inserting bee products and drones into my therefore designed subnetwork.
Transfering items from one ME network to another:
Stocking items used by other mods/automations/whatever:
Other one is for fuel, third one for unloading flowers(could do with 2, but programmed it this way so script could run with just chests).
More transferring items from one network to another:
This time controlled by item levels.
Automatically keeping items in stock:
ME precise export bus set to "Craft only" controlled by Level emitters, ensuring certain items are always kept in stock in the network(for example making sure to craft ME interfaces so there are always 10 in the network should I need some
).
Forestry Multifarm exporting its items directly into the ME network through Interface: