I'll start off with the most important question: is it worth it? My answer is yes it is worth it, but it could have been a LOT better than it was if the writers made different decisions story and character wise (i'll get into that later). Overall the acting was great from Lee Jong Suk and Kang Sora, and the story was very interesting from the beginning to the almost end, but I am unsatisfied with some of the story choices.
Mainly with the couples. The chemistry between LJS and KS was undeniably strong, I was literally drawn to them and that was the main if not only reason that I was so engaged in the show. On screen it almost seemed obvious that they had mutual feelings for each other, but instead the writers decided to have him choose his first love, and while they were cute when they were younger, their chemistry was a lot less and more bland then his with KS. That was just poor writing in my opinion , and it just makes LJS's character seem like an asshole for flirting with KS when it seemed he had more feelings for her then he did for his first love. I'm still waiting to see LJS and KS on another show together...