I use Nonghyup and it was fine for me. I've only done it twice, and the first time it cost a lot of money because I did it online and must not have done something right. I definitely recommend going to the bank every time you do it, and make sure you have an English speaking banker (they do exist, so just makes sure to ask for one, or come back when one is there). You can chose to have the banker take the transfer costs out of your local bank or your bank at home and I think my costs were no more than 30,000 won all together (maybe less?!?). Also check to see if your bank at home charges a lot. Mine charged a transfer fee from an intermediary bank and my bank so it cost more the first time ( i fixed this by transferring to a different bank account at home). I know i rambled a lot so if you have more questions ask me, but mostly, just find an english speaking banker and you'll be fine!