It's a great podcast. Starts out a bit wobbly, but gets better and better. Once you finish it, there's also his Revolutions podcast, which has so far done series on the English Civil War, American Revolution, French Revolution, Haitian Revolution, Spanish American wars of independence, July Revolution, Revolutions of 1848, the Paris Commune, the Mexican Revolution, and currently the Russian Revolution.
He's ten episodes into the latter, with many more to come. That will be the last series, though. Hopefully he does another history podcast after that, and doesn't just commit full-time to writing books.
Is he as good as Dan Carlin?
He's much better. Dan Carlin tells a better stories, but Mike Duncan goes into much greater depth. If you listen to a history podcast to learn history, Mike Duncan is the guy.