Pros
Once you get the hang of class prep, it takes minimal time & effort, as the academy provides the lesson plans. Mind you, there is a bit of tech to familiarize yourself with (specifically smart boards), but isn't difficult to get used to. I have heard a lot of complaints regarding the work-life balance while working at an academy, but in my opinion ESL teachers don't realize that they are working less hours with less pressure from management than the average Korean white collar worker.
Cons
Summer & Winter intensive classes call for ~11 hour work days. Extra pay but a lot more teaching during these weeks. Quarterly report cards can take some time if you don't work on them in advance. Vacation days are set and not for choosing (at least when I was working there).