My feeling is that PBS and NPR take a classical liberal stance when giving opinion and a centrist stance when reporting news.
You will seldom witness support for creationistic science, anti-abortion, less government (regulation of business), anti-homosexual, pro-nation building (or influence thereof), religious dogma in public schools, and any of the other pet projects of the far(ther) right-wing.
I appreciate the News Hour extended clips and discussions.
Most of the series are top-notch and beat Discovery by country miles, IMO. The single-video one about physics and the Big Bang theory finally made me understand what the heck Stephen Hawkins is talking about. The one about plate techtonics was an eye opener (image of the earth with the cracks in it like an egg).
When I have money, I always donate to both operations. If we go back to all-commercial TV, then I guess I'll just have to shoot mine.