For me it was very good drama:
we have scenes that's make you laugh so much that your stomach ache,
well-recorded scenes and
good matched music.
The love/hate relationship between the Monkey King Son Oh-Gong (Lee Seung Gi) and Devil Ma Wang (Cha Seung Won) is so funny. Love this two acting.
And we can't forget the character of Zombie girl :). I give lower points for acting because of main female lead. It wasn't nothing bad but my personal feelings.
If you want someting light to laugh with good story, then this drama is for you.