I love that bar, I don't even need to bookmark pages I visit a lot any more. All I need to do is type, say, "yc" and up pops this site. "tv" will show me tonight's TV listings. "gu" brings up the Guardian.
If I wanted to come back to this story, "yc firefox" would most likely bring me here and to any other HN stories I'd read with Firefox in the title. And so on. I didn't really like it when it was first brought in (change? no!) but it's grown on me.