TL:DR, nice effect, there is not a character around that doesn't want this in their deck. Problem is that a free action, at that cost and a cardslot, probably not be what the doctor ordered, therefore it'll rarely see play.
Swift Reflexes is a free action, it even gives you some leeway in when it happens, sneaking actions into someone else's round, useful for example to grab an enemy or snipe a persistent encounter card so that another character might do their thing better. An extra attack, a move, actions are good.
But the problem is the economy, you get 3 actions per turn for a dozen+ turns every game "for free", paying 2 resources and a card is steep but fair, but can you spare the card slot?? You need those slots to build that carefully orchestrated deck, how valuable is that lone bonus action over, say, an extra card draw from a boosted action with one of the neutral skills on it? Do you have enough weapons? Most cards are about generating extra success value from every action, "More success in less actions", a flat +1 action is therefore weirdly often unhelpful, at such a steep cost that is.
It's not a bad card, it's mostly a case of an effect that in of itself is so small that I wonder if it'll be worth it's slot, at that price too. I would be glad to see an XP version that grants some bonuses during that extra action.
Edit: Some more experience.
I started finding more use for this card, mostly outside the faction. folks tend to pay through the nose for stuff, especially , which is where non-repeating extra actions really shine. Characters with large bonuses already will find Swift Reflexes much more routinely useful then those with 3 or less. Tony Morgan and Leo Anderson for example.