Has anyone bought from Great Courses? Are they any good?

This isn’t spam – this is a real question.

In today’s mail there was a course catalog from Great Courses. They sell self-paced learning CDs and DVDs on a variety of subjects – everything from religion to photography to astronomy.

The professors (speakers) appear to be of reasonable stature—I’ve heard or read of several of the presenters.

My question: are these courses any good? meaning: well organized, in that they present what they say? Comprehensive?

Any comments, positive or negative, would be appreciated.

[For what it’s worth, I’m considering the course called “Think Like an Economist”]