The only way I can even begin to describe this drama is as a 'wasted opportunity.' Now, it wasn't 'bad' by any means, but that also doesn't mean that it was the greatest.
Doctor Stranger had a very intriguing beginning that captured the viewers attention just by the mere mention of North Korea. With such a strong beginning it is almost impossible to think that this drama could even go downhill; however, this a completely wrong assumption to make. At the start, the focus on Park Hoon and the moral dilemma of being a doctor made for a completely emotional story line. Unfortunately, the show was not able to keep up this interest as it feel into a decline. The romance was dragged out between the main character and his love interest with too much push and pull that made it quite difficult to end up rooting for them (especially since their romance as childhood sweethearts was too adorable to handle). If you are looking for the romantic doctor content, then you most likely won't find it here. The biggest issue with the story line is that it just wasn't planned out as well as it could have been.

Acting wise? Not many complaints. Lee Jong Suk provides amazing depth to the lead character and acts with the same charm that we all know and love. Park Hae Jin's double sided character is portrayed as well as it can be within this drama, no complaints. As for the two female leads, it is hard to say whether they were good as their characters were just terribly written. Many scenes with the female actresses were just missing the character development that they both deserved which in turn just made them bland and uninteresting to watch. I think it is safe to say that Yoon Bora's Chang Yi saved the day in terms of female characters with her lovable and charming personality.

Can't say much about the music as it did not seem to have as much of an impact as it should have.

Would I rewatch it? Probably not. Would I recommend it to someone? Possibly yes, depending on if they are a fan of any of the actors/actresses.

Overall opinion: I am not going to say that it is the worst (even if it was, I can't leave a drama unfinished). But there are definitely places for improvement, which is disappointing because the show had so much potential if it had been executed properly. My positive opinions about the show come from a bit of a biased opinion based on the pure fact that I am a fan of Lee Jong Suk and Park Hae Jin. If you want a romantic drama, this isn't the one to look for. If you want a medical drama, there are a few better ones out there. If you want good looking male leads who provide depth to a character, then knock yourself out with this.