I've been lurking on this thread last year, then coming again from time to time to enjoy some of your interesting comments. I'm about to watch the show again soon, so I feel already excited about it.
Duel is one of my favorite dramas ever, if not my ultimate favorite. I've been hooked since the first episode. I've found myself drawn in by the gripping plot and directing, and by the endearing characters, so deeply that I'm still thinking about this drama a year after I've finished watching it. I love the way the plot unfolds, especially starting from episode 8, when Sung Hoon is starting to lose it. I don't agree with some people here that the first half is better than the second one, I feel that everything is well-thought from the beginning to the end. Since it's a human drama above all, the second half is the real heart of the story and it delivers superbly.
The character development and acting in Duel are excellent, leading to some of the most emotional scenes I've seen in a drama - which is very unusual for a crime thriller drama to say the least. Watching Duel is a unique experience, and I recommend those interested to bing-watch it as much as possible to feel the rare feeling of emergency that it displays all along.
Well, I love everything about Duel, and I'm of course utterly impressed by Yang Sejong's mesmerizing acting performance. I wonder when I'll be able to see a performance of this caliber again. Not just in a Korean drama, but anywhere. Since he is a rookie in this drama, he doesn't care about his image and gives his characters his all, if not more. His unbelievable talent mixed with the freshness of his characterization makes a strikingly fascinating combination. Sung Hoon's character especially is unforgettable, he is a superbly written character blessed by an outstanding incarnation from the actor. Just wow.
Honestly, I don't even understand how you can claim to have an opinion about the drama's "focus" when you watched it from the second half, missing about 8h30 of its intrigue, pace, directing, acting, editing choices and so on. It's not the first time that I see someone thinking they have seen a drama or a series just by reading "recaps" of the episodes. Reading recaps and watching a fiction are completely different things. Some people love to read recaps for the reason that these are written from someone else's point of view. The recap is not neutral, and doesn't render anything about the moving object (the movie/drama). You have to use your own eyes to be able to give an opinion and not just "guess" what the writer wanted to say.
Duel's plot does have focus from the start and it is not confusing at all if you stay... focused. The pace is fast but the drama knows where it's going. There are very few unanswered questions at the end. Maybe it's just me but being used to watching a lot of movies, from art house to hard-core action movies or sci-fi, I don't feel the need to have every single detailed "answered", especially in sci-fi /fantasy genre. Some elements can be left to our imagination, it's also part of the fun. Duel gives a satisfying ending in terms of connecting the parts together, and most importantly, the characters are very consistent and beautifully developped.