These new notes are a nice change to the old ones as they they are smaller and look much better. The vibrant colors remind me of Canadian currency from back home. One thing that I have yet to figure out, is why the 10000 won is the highest denomination. It makes for a fat wallet if you're carrying around large sums of cash. Although there are 100 000w "checks" you can get at most banks, but that requires going to the teller.
Take a look at this picture below and see for yourself the difference between old and new bank notes. The 1000w changed from a pinkish purple to a light blue. The 10000w changed to a brighter shade of green. The 5000w note has been out for a while. Notice how the lengths of each bill are different. Slowly but surely the new bank notes will replace the current worn out bills.
If you're considering teaching English in Korea, you might want to familiarize yourself with Korean currency. The coins are as follow: 500w, 100w, 50w, and 10w (equivalent to an American half dollar, dime, nickel and penny).
The point I am trying to make is that if you want to become a millionaire, come to Korea! You just might find yourself carrying a cool million or two (won that is) in your pocket. ;-)