This drama, for me was kind of like a look back into my childhood.
My favorite show of all time is Ghost Whisperer, and this show brought back a lot of feelings for me with that. Especially with Bong-Sun being the way she was in the beginning.
The first time I watched this drama, I quit at the first episode because it made no sense to me whatsoever. Then, going back after watching a lot of kdramas, this became more enjoyable then a lot of others I forced myself through.
To start out with- here is the things I enjoyed the most:

-->Soon Ae towards her brother.
Do I need to say more? As I was pissed on how her brother mistreated everyone, I was taken back by how everyone was affected when someone came into their lives that reminded so much of someone they had lost. I love in KDramas how sisters usually slap the brothers on the head countless times. It is what makes a KDrama a KDrama in my opinion.
 ---> The drama teaches a very valuable lesson you don't often think about. That if you were killed and didn't know how- would you want to know? Would you have changed it? If you were murdered or raped, would you want to relive that as a ghost? Would you want to see the person who killed you?
Or, say you died in a car accident. If you were upside down in your car and couldn't get out- and your loved one just found out and came to somehow save you with firemen, would you want to perceive your death as no one coming because of a blocked off intersection/ bridge broke down, or possible bad guy ((such as in OMG)). OR would you want to perceive your death as watching your mother/ and or father reaching out to you. A simple act of someone really important in your life there to save you.  It is that lesson that is very important in this drama, and something I think about very often from watching this.
==> Now lets apply this to OMG-- When Soon Ae found out how she died, would you yourself want to know what happened? Or would you  yourself just want to get rid of whatever grudge (if you are a virgin, etc) and go to heaven. She was curious the entire drama on how she died, but she had hesitation. What if it is something bad? She didn't want to know at first, because she couldn't go back and fix it and live again.
---> Going on with that, this drama also did a good job on the question if people still care after you die. That people still live on with their lives, and Soon Ae took a while with herself to comprehend that everything was the same-- nothing changed. I loved her character in that regard.
-->Less corporate mumbo- jumbo talks that take away from the actual story itself.
-->More talk less showing of mother's wealth. Many dramas show instead tell of wealth. This can be overpowering to watch, because you get (in my opinion) less emotion and personality out of the characters. Poorer characters DO have a hard time, but they are more likely to make the situation brighter in some aspects. (If you have no idea what I mean by this, just look at the characters in Manhole. He's living in his parents house in the beginning and is still happy with the small amount of money and friends he has. Instead of other worries, his only worry is getting his dream girl to like him-- not to move out ((unfortunately lol)) ).

--> loved the shyness of Bong- Sun. Yet, I sometimes couldn't handle Soon Ae's childish persona when she was Bong-Sun. I really don't know.
-->Officer Choi can leave. Greedy, greedy boi. (( In my personal opinion, Im Joo Hwan is an actor I hate mercilessly. he himself must be a sweet person, but his characters just ruin every drama for me for the worse. Uncontrollably Fond was horrible because of him. I loved Suzy, but couldn't stand him. Anyway....))
-->Seobinggo. ?? Never understood her character. Even though she is supposedly a fortune teller, I thought she was someone from up above getting her and didn't realize she was real for a very long time. Her character was always back and forth for me idk.
and lastly
-->I didn't hate the other cooks, but didn't like them either. Some times they were funny- some times they were just annoying. I don't understand how they didn't catch on with Bong-Sun but whatever. Nothing to think too hard about.

All together, the lessons I've gotten out of this drama is really amazing. With the couple flaws it does have- it will remain one of my favorite dramas.