I'm pretty sure the standard thing for most people here is to replace it with one of the universal ATFs out there, and I've been using Mobil 1 for years now and it has always worked the same. I don't see any cons to using synthetic since it is well proven that synthetic is better in every way except for price, and with the amount used in the power steering it won't be very expensive either way. If you suck up what is in the reservoir with a turkey baster or fluid pump then refill every time you change the oil you won't have to worry about the P/S fluid getting too old.
"Formula 1 is better than NASCAR... If you compare them to musical instruments F1 is a Stradivarius violin, NASCAR is banging a saucepan with a wooden spoon." -Jeremy Clarkson