A good free MMORPG, just don't expect it to be mindblowing...
The graphics in KO are good, but nothing spectacular. The land and creatures are good enough, but you won't be blown away by them. You can tell the game uses the same textures over and over, as some of the land and buildings look kind of meh. But, for free, what do you expect? The sound is also good, but nothing spectacular in that department either.
The gameplay in KO is good, but not amazing. Theres a lot of level grinding, but the combat is fun enough so it doesn't bother you that much. There are a lot of unique moves you will gain as you gain levels, but the problem is that theres not that many classes to choose. You will see a lot of clones, early on especially. There are some cool weapons and armor in the game, rewarding you for spending the time to get to those high levels.
All in all, KO is a good time for being free, just be sure to realize before playing that you get what you pay for.