For the most part I enjoyed it. (Mild spoilers follow)
There were some noticeable inconsistencies, but they didn’t alter my enjoyment of this drama. What did change for me as the drama progressed, was that the “great” love between the two leads never really transpired for me. I was more into the back story of her first great love, and in hoping that she and he would have the opportunity to find it again. Of course I knew on every level that it couldn’t realistically be, unless her current love was a reincarnation of the first one. I honestly felt more longing and more of a connection between her and her first love.
Then, although the drama is based on goodbyes and moving on, there were just too many goodbyes in the end, and long ones at that! I kinda got the feeling that they no longer knew what to do with the leads by then, so my interest waned. Also, you really had to suspend belief in some of the situations and scenarios. I really liked most of the characters though, their histories and the bonds they formed. I cried more than normal, for me, lol.
I still look forward to seeing the leads in other dramas, and I especially enjoyed the stylish wardrobe of IU!