Very unpopular opinion here, but it's just my opinion -

I love Ji Sung - he is such a talented and charismatic actor. I don't know why I kept putting this one off, but now I wish I had continued to keep it on the back burner.

There was a lot to like about the show:
1) Ji Sung
2) Second couple - they were just so cute
3) The entire pain management team was fun to watch. They had the ability to be serious, but there was a lot of levity from them as well.
4) I loved the fact that the hospital politics was low, and we got more focus on the doctors and the cases they handled.

Now the causes for my mumbling:
1) Lee Se Young as Kang Shi Young. I have liked her acting in other works, but she really bothered me here. This character cried in every episode. She was kind of a stalker toward Dr. John and followed him around a lot. For being a resident, she had an awful lot of free time! And the strange haircut...when they first showed her at the conference from the front, I thought she had a bob haircut and it looked really cute. Then she turned around, and it WAS a bob, just with a lot of long hair underneath it. It was so distracting! Add her wide-eyed staring at Dr. John all the time, I didn't like her at all.
2) The romance. It should have been left out. I love me some romance, but the leads had absolutely no chemistry with one another. I think that this is the first time I've watched supposed romantic scenes and been uncomfortable. They acted like they were acting, and I didn't believe that they liked each other at all.
3) Do medical shows have medical advisors? If so, the advisor for Dr. John must have been on vacation when they were filming.
A woman has had her arm amputated and feels pain - she knew nothing about phantom limb pain?!?! They warn amputees about this. She thinks that he has a fever, and she checks his forehead with her hand. She checks his pulse with her thumbs.
Multiple instances of patients writhing in pain with no medical staff close to them and the side rails are down. She's worried that he's gotten this dreaded disease a few hours after contact when she's already told us the incubation period was 10 days.
They stated that the actress had not signed a DNR form, and then were yelling when he was performing CPR. And can we talk about how fake the CPR looked. Get the disease names right - it's lymphedema, not lymphadenia (maybe a translation error, I'll give a little slack on that.) There is no way they would have hired him back at the same hospital after being in prison. Him not being able to feel pain, there is no way he would have been walking around outside barefooted, at night especially.
4) The last few episodes. He leaves for three years without contact. She CONTINUES to try to reach him (have a little pride, woman!). Come to find out, he's been back for a year and following her around, then he shows up in her face and she just forgives him (she's crying of course).

I had high hopes for this, but the writing took a definite turn in the wrong direction somewhere along the line.