No more balancing check books.
Just stick your bank book in the ATM, and you get an up to the minute, accurately balanced bank statement.
Need to pay a bill or send money to a friend? Just input their account information, press a few buttons, and it's in their account. It's like magic.
Korea's electronic banking takes a little getting used to. But it will be hard to go back to the dark ages of filling out checks and then flipping to the register and writing the info in those tiny little lines.
(Thanks to Ron Knickerbocker for reminding me about this - one more thing I'll miss about Korea.)