Pros
EPIK gives the best contracts, hours, and most stable employment of any English teaching job I know of in Korea except a university teaching position. Teaching in a public school is a real Korean immersion work experience. I got to witness firsthand what life is like in a Korean school. Work starts and ends at an early hour, leaving time to do what you want every evening. There is the obvious opportunity to stay long term in a new country and explore what life has to offer there. Depending on your co-teacher and school, you will have a lot of flexibility to prepare your portions of the class lessons and plenty of office time to get ready or just relax and do your own thing. There is a generally higher standard of teachers in EPIK, so there is somewhat better reputation and peace of mind to be teaching in a public school.
Cons
I was placed in an apartment over an hour from my school. My morning ritual of switching between bus and subway lines was so miserable and time-consuming I wanted to quit as soon as my first year contract was up. My school was in a bad neighborhood on the edge of the city, and every teacher commuted a good distance to get there, so whoever chose my contractual apartment for me found one n a district where "there are a lot of foreigners" and some other teachers at my school lived. They had cars though, and I was not at all a high priority, and being that the Korean way is to abide and not complain and try to assure one's superiors that everything is well, I don't think it ever occupied to anyone that my living and transportation situation was awful and really spoiled a lot of my experience there. So be prepared to possibly get put in a school that is seen as a low level, unattractive school in a very out of the way location. It really is a roll of the dice you're going to have to make do for a year. My first co-teacher flat out told me she was tired of teaching and wished she had chosen another occupation. I think that getting along with your co-teacher and having a professional co-teacher who runs a disciplined class is crucial to your enjoyment of teaching and generally your Korean experience. You can try to use your best teaching and personal communication and conflict resolution skills, but don't expect to have much success. You are the foreigner who is appreciated as a novelty, not a co-equal whose voice will be respected and followed, and the horror stories abound of bad co-teachers and principals who just don't budge on irrational and burdensome decisions. During the students' summer and winter vacation, you are still expected to come to school and sit at your desk all day. It is completely absurd and without good reason, but being Korea people just say, "Yeah, that's Korea." I sometimes sat alone all day like "The Shining" in a freezing, quiet, empty building without seeing another teacher all day (only a few other teachers ever had to come to school during vacation). Don't ask me why the least regarded teacher, the Guest English Teacher, had to be there. The overseas experience would have been MUCH better if the school vacation time were extended and made standard for teachers across the city or region. You don't even know what days you get for personal vacation until your school and co-teacher decide you will have your break time English camps. It's a big mess that I think everyone agrees needs to be cleaned up.