I have only seen him in one movie, and one KDrama. But from what I have seen, I like. He is great at acting and adorable while doing it. I would love to see him in more movies in years to come. I recommend you catch him in the movie 100 Hundred Days with Mr.Arrogant. Kim Jae Won is definitely an actor to keep an eye out for in my opinion.
His skill shows in the way it just seems natural when watching him. I have seen other Dramas where some of the actors it seems forced and so unreal, but with him it isn't that way at all. He is pleasing to the eyes and ears.