Now that the janky applications of this card have been officially ruled out (no, he won't let you solo a scenario without ever drawing an encounter card... and no, he won't make your deck weakness free...), it's time to take stock of what remains. So what does this fusty, jittery, bespectacled old bookworm have to offer?
In short, money. Cheddar. Thick wads of cash. Sacks of doubloons splitting at the seams. Once per turn, whenever you draw a card, you can instantly discard it for three resources. How good is that? Think of it this way: Armitage turns every card in your deck into an actionless Emergency Cache. Absorb the magnificence of that: you now have 30 lovely cards in your deck, doing all kinds of lovely things, which can ALSO be played as FAST Emergency Caches... Armitage is the King Midas of allies: whatever he touches turns to gold. Simply put, there is not a card in the game that can match the income-generation of this creaky old Croesus.
Of course, one hardly needs to spell out the uses of an enormous resource flow: every player has their own fantasies. Expensive assets, fodder for your Streetwise, the world's buffest Money Talks, whatever you like!
Oh, and just in case all that wasn't good enough: in a pinch, here's your third copy of Unexpected Courage.