Yes, they've done some scientifically interesting work. But in relation to the money they've spent on it, they have made very few obvious technological advances since the days of JFK.
Some of the exploratory work has been very interesting, but we're no further forward with the basic mission of getting into space. They have spent far more money playing PR games with the Russians than they have on the basic mission.
As it is, sensible people have had to fight with them tooth and nail even to get them to do such low maintenance things as keep the Hubbard telescope going, because they'd rather help another Soviet astronaut get up to a decaying and purely symbolic space station.
It saddens me how anti-science a lot of people are. Just look at the COBE and other background radiation data is. It's actually basically worth any cost. And it's *especially* worth it considering what a tiny amount NASA is of the US GNP.