"Death Valley Queen" is the biggest ripoff of The Pogues' "Turkish Song of the Damned" I can imagine. Therefore it's a great song. :-D
I seriously love both bands, but for different reasons. DKM can do street punk much better than most, and I think for them the celtic elements are an embellishment that makes them disctinct, but doesn't have to define them. Flogging Molly are more in the tradition of the Pogues or the Tossers, but with louder guitars.