The same friend of mine that borrowed my Batgirl runs of Cassandra and Stephanie introduced me to a friend of hers that's into comics. More Marvel than DC. He was surprised there was more than one Batgirl. When he asked who my favorite superheroes were I went down a list then said there was one but I doubted he knew who it was. I said Booster Gold and he nodded saying he knew who that was. After I expressed my disbelief my friend and him both said Boosters' slogan in union.
So in short other Batgirls aren't known to causal fans but Booster is. It's not shocking per se, I know Barbara is the one that's always pushed but it's also amazing that Booster is more known than something from the bat books.