KakaoTalk Messenger puts a really exciting spin on the free-text app by adding fun icons and a great layout. The only problem is that it doesn't really seem to have caught on very well. It has enough going for it that it might be worth sharing with your friends, though.
You can only chat with your friends if they've already signed up for KakaoTalk. During testing, it only found two people from a contact list of hundreds. For what it's worth, KakaoTalk Messenger seems to be more popular in Korea, with many top Korean celebrities having accounts. If you do find your friends, you can do a solo or group chat with them. You can also add animated icons, but many require you to fork over some real money. There are some cute ones, but a lot of them have that sickeningly-sweet Hello Kitty aesthetic. Call quality is decent, plus you can optimize the app from the settings menu. From there, you'll find some advanced notification settings and the ability to change themes. You can even create your own themes on the fly.
A chat app is only as strong as its users, and this one is lacking in that category. It makes up for it with lots of cute icons that will go over well with a certain crowd. If you can convince your friends and family to sign up for KakaoTalk Messenger, you might have a good time with it.