I would call her a great under-sung heroine of the musical theater, but she's highly respected, and deservedly so (witness this post and thread).
I would assume that her decision to move to Seattle around 20 years ago--and, aside from occasional returns to New York, largely center her career on the West Coast--is largely why she isn't the big Broadway name she could have been. But she has said in many interviews that she is content with the choice she made. I think she's truly one of the three or four finest female voices on Broadway in the past 30 years.
"You travel alone because other people are only there to remind you how much that hook hurts that we all bit down on. Wait for that one day we can bite free and get back out there in space where we belong, sail back over water, over skies, into space, the hook finally out of our mouths and we wander back out there in space spawning to other planets never to return hurrah to earth and we'll look back and can't even see these lives here anymore. Only the taste of blood to remind us we ever existed. The earth is small. We're gone. We're dead. We're safe."
-John Guare, Landscape of the Body