very few people push on the flop with a set, unless the action is real crazy. Even the most aggressive players are looking to extract money with that.
Two pair is never the nuts, but it is definitely a strong calling hand.
edit: I also busted out of a live $.50-1 NL cash game a while back with top 2 pair, the guy set me all in with an OESD, and I beat him into the pot with the call. He hit on the river though.