I took a course in my undergrad for fun. It's an interesting design paradigm, all the code had a built in schema attached to it, if I recall correctly, which I've come to appreciate and find more interesting over time.

Using the AS400 was very interesting as well.

The problem about COBOL, for me, is it's so specifically designed to fill a niche of business record processing, that I'd never use it for a side project. It's too verbose, and too restricting.