My 14-year-old son, wife, and I watched the entire series. My son, after a less-than-interesting year of American history in school, was not only interested, but excited about watching every new episode. There were a great many details about American history which are often glazed over in textbooks. I would not call this series an overview of American history, nor do I think it really attempts to become that...rather, it does a fine job of pinpointing some rather important, lesser-known events that greatly affected the direction of our country.
The computer animations, at times, were poor...though I've seen blockbuster movies pushing the limits and doing little better. The side conversations and interviews with modern celebrities were interesting...at times very relevant...they were always brief, however, so even when some seemed a bit pointless, they were not really all that intrusive.
If you have the chance to view this series in its entirety, and you are not an American history expert, I am certain you will learn a great deal in every episode. This series cannot be expected to be a standalone summary of American history, but it really is a great supplement to what you might already know and does a good job of actually avoiding hitting those topics which are usually taught in excruciation detail in a class setting (eg. Civil War battles).
Update 1 year later: My son is completely interested in history class, and the topic of history, in general. He is not considering any career in the field, but thoroughly enjoys discussing detailed points of the topic with peers and adults. I fully attribute the spark of his interest in this topic to this mini-series.