At first, I can honestly say that I watched Arang and the Magistrate simply for Yoo Seung Ho's prettiness (c'mon, he was rocking the Barbie hair and the Chinese robes!). However, I soon started watching it because of the show itself. The story was quite exceptional and the plot was quite original in my opinion. Arang is about an amnesiac ghost that requests the help of the city's magistrate to discover her identity, and her eventual murderer. Each character suited his/her role (especially Lee Jun Ki- his fighting scenes were kick-ass!). The supporting characters (Bang Ul Ri and Dol Soe) added a lot of heart and laughs to the story. Of course, the music selection was amazing; I had goosebumps during the creepy scenes and chills during the romantic scenes XD. The directing was top notch and the script kept me hanging for each episode. I was dying for Wednesday and Thursday to come around every week. :P
On the other hand, the actors were not exactly mind-blowing, except for maybe Eun Oh's mom. The rewatch value is sorta low because the drama is mostly suspenseful, and all that suspense would be gone if the drama was rewatched.
Over all, I would say give Arang a go, though! If only for Yoo Seung Ho's hotness ^__^