Update: Now having watched it all, this drama does not disappoint. The complex plot is handled extremely well, the drama answers the questions it raises but manages to keep you in suspense right to the end. Despite the fantasy plotline, the detailed and rich characters make the show feel amazingly real.

The writing/direction/production team all paid close attention to detail and crafted both scenes and sets with clues and forshadowing that make it the perfect sort of show to rewatch.

For anyone who is into story analysis, it struck me in the closing scenes that they wrote a Hero's Journey into a romance plot (not along side it, but literally, the romance IS a hero's journey), which is really something amazing. I can't say I've ever seen it before. So, I feel like it's not hyperbole when people say this is the best show they've ever watched. It's pretty amazing.

(Original review written around episode 8 below):

There's so much going on in this series that I love. The writing is tight, well paced, and presents at the same time a fascinating puzzle of a time travel story; a deep reflection on grieving; a thriller-type murder-mystery; and a double romantic comedy, played out in different timelines. It is genuinely a cross-genre show, so don't go in expecting pure comedy OR pure drama.

The acting is fantastic. I have always thought Alice Ke was an exceptional actress and she's not disappointing here. I liked Greg Hsu in Love Storm, and he's even better in this. The whole cast is great, but these two really shine. Directing. It's brilliant. Together, the writing and directing are letting the mystery of the time travel as well as the murder unfold in a way that raises new questions as it answers old ones. The directing includes so many little details that not only draw us into the mystery of the time travel, but hint at the more overarching explanation of what is happening. There are nice little symbolisms, like the red earbuds that the leads share at times, which creates a red thread linking them. There are also many conversations and dreams that we see early on that take on new meaning as the story unfolds, giving a sense that all the details matter... there's no filler here.

There are some more ambiguous symbols as well. There's some significant representations of enclosure and separation/isolation. These could represent grief and loss, which is a major theme in the drama, but they take on additional potential meaning in terms of what is really happening... that there is loss, grief, and perhaps the potential to heal or even change the past is a given. But what isn't given is that what we see is the actual story; many of the symbols reinforce the sense of fragmented reality that the female lead experiences in both her grief and her early experience of time travel.

For example, the "broken audio/video" shifts between scenes, especially with time travel, play into the fact that in the first few episodes the transition from an ordinary story about living with grief to a supernatural story about time travel/fate is started by the use of technology, once to find a "doppleganger" and the second time to use virtual reality to "reunite" with the lost love. While nothing much is made of this (and as of the 8th episode, it hasn't become a factor), these sorts of hints are beautifully done. They make it harder to guess the overarching explanation while at the same time they work on their own. That is, if it turns out that they were never anything more than a couple of scenes in the first few episodes and had nothing to do with the over-arching story, they still work. They aren't just red-herrings to obscure the truth, they are integral moments in the character development and plot that *could* mean more.
Long story short: it's fabulous, and given how well done it is so far, I'd really be surprised if it stopped being fabulous.