Downright brilliant! Cogent, understandable explanations of the workings of the cosmos from a crew of distinguished and very personable experts. The two seasons narrated by Erik Todd Dellums were very good; he's a highly skilled narrator. But, for me and my wife, he just ain't Mike Rowe. Rowe has a neighborly and honest quality in his voice that inspires confidence. And it doesn't hurt that the scripts he reads are uniformly excellent clear, engaging, and wonderfully instructive.
Oh, yeah. One other reason to watch How the Universe Works: To see what resolution, brightness, and color rendering your TV screen is capable of. The graphics of this series are not only brilliant and dramatic, but the picture is astonishingly sharp - darn near 3D! My many years-old 42" Hitachi is surely not "cutting edge" but the picture it can produce of this series is so very good that I can see no valid reason to buy a TV that is larger, slicker, and more expensive.
The only criticisms of this series are, first, the scientists' constant anthropromorphizing every cosmic event. I realize that for some viewers, a series applying human emotions to every celestial event makes the subject more "down to earth" and, possibly, less daunting. But no stars are actually vampires and Jupiter doesn't deliberately protect the Earth from homicidal asteroids. I'm perfectly comfortable with such rhetorical devices as "the Goldilocks Zone" and cosmic interactions viewed as pool balls scattering form a good solid break. But let the brilliance of the graphics and the genuinely instructive parts of the scripts do their jobs. We viewers don't need a group of P.T. Barnums with Ph.D's.
My second gripe is that every year's episodes are not currently available on DVDs. Obviously, that is the result of the marketing department. They're all accessible via streaming video, but some of us would like to have our own copies of those episodes.
This "keep it running on TV because that's more profitable than one-time royalties from purchases of DVDs" strategiu may be sound marketing, but the results can be downright infuriating. My wife and I are addicted to "World War II in Colour", narrated by Robert Powell. It's been on the "Heroes' Channel (nee "the Military Channel) constantly and we enjoy watching episodes, even those we've seen multiple times. But DARN IT, I want that whole series so that I can watch whatever episode I want when I want! I see ads for the whole series, but they're either a completely different "World War II in Color" or they're the right series but available only on DVDs that won't play in American DVD players.
Rant over.
Bottom line: "How the Universe Works" is some of the best science education available anywhere and is a great deal of fun to watch.