I am a huge fan of the original masterpiece (Taiwanese) version of this remake and I have to say, if you watch this with the other one in mind you will be greatly disappointed.
But if you watch this with fresh eyes or you aren't interested in the original you will find this one entertaining and enjoyable and filled with lovely moments.
Best thing of this remake was hands down the female lead, Jeon Yeo, her capacity of transforming herself into the two personalities (Jun Hee & Min Ju ) was amazing, I was in awe every time I was watching her one or the other you could tell who was who immediately! Really good performance.
Not that impressed by the male lead, I watched him in a lot of dramas ( 17 going to 30 my fave so far) and he is a great actor, but I am not sure if this was how his characters were written, or because of the consequence of the time travel and the mix of the personalities, the two characters were so similarly played (Yeon Jun & Si Heon) I could barely tell them apart.
The romance of the drama is good and is a big focus of the series, I felt the chemistry between the leads and it was quite enjoyable for me to watch this remake with this actors as well.
Time travel arcs of the series, along with the crime, thriller and suspense ones , had some holes and some parts made no sense at all, so it gets to a point that you just keep watching and go with it. That was a bit frustrating.
Overall and I say it again, in my opinion you will only be able to enjoy this drama if you don't compare it to the original OR you haven't watched it yet.
So if you haven't, give it a go!