DISCLAIMER: This is my own opinion. No harm meant to the fans. The drama is bad NOT the actors!

If it had not been for the Watch Challenge this drama would have ended on my Not Interested list (where I put dropped dramas!) after the first episode. Since I promised to finish it, I used my time while watching to stop and rant which you can find below.

In short, this drama has not aged well and it is only 8 years old. The story idea is good, the acting is stellar, the production values are correct. And the writing is catastrophic: EVERY single character starts and ends as unlikeable (with the notable exception of three kitchen assistants), the WORST character ever in k dramas being the sous chef, a misogynist and sexist (he does not want to employ a married women with a kid! this was never ok or funny, as they used it here!) harasser. He might be a good cook but he is a despicable person. The main couple has no chemistry and the character development for the FL turns out to be the complete character change as in she takes all the traits of the ghost girl's personality together with the annoying baby cutesy voice!The plot is full of tropes, it is highly predictable (the murderer was obvious in ep 3). and therefore very boring.
I never watch anything in high speed so I only thought about ffw towards the end of ep. 15. Too late!

The music was correct, especially in the first half which was supposed to be a comedy and they used a lot of jazzy tunes.

THE RANT
I am spending more time ranting about this drama than watching it. I wanted to like it so much but, unfortunately, it is so bad. Ghost stories, possessions and romance are the tropes I like but here they completely ruined it with extreme characterization!
First of all, what is with this woke title on viki: Oh My Ghostess? I did not know the word existed!
4 episodes in and I am not really liking the drama: not a single likable character and everything seems to be set up as extremes. I guess they need to show the character growth but seems very predictable and cliché. I hope I am wrong....
One FL is a doormat, the other pushy harasser as a ghost but a cheerful optimistic girl in reality, the ML is arrogant, his mother annoying, the cop obviously a bad guy who killed the girl and no one knows how to say NO when even slightly pushed.
This drama is so full of tropes! I really hope it gets better!
Ep. 5 and the ML goes topless in order to put some skincare on his face! Nice; Good opportunity for the ghost girl to make a lot of lewd sexist remarks we are supposed to find funny and cute. Imagine if it were a man doing the same thing? Not funny at all! I can go with the idea that as a virgin ghost she needs to get rid of her virginity (how does that work, I wonder?) but does she really need to talk lasciviously?
Ep 7 we see the original, super shy, introverted and incompetent FL freed from the possession and the ML liking her more and more. Does she remind him of himself in high school when he was shy and bullied? But he likes the ghost as well because she's fun and extrovert, good cook and quick thinking!
A pet peeve of mine when I watch dramas set in restaurant kitchens is that almost always the female characters cook with their hair freely flying around: so un hygienic! I know, a FL with her hair tied or under a bonnet is not very appealing but still....when I see them like that, all I can think is "hair in my pasta" and not "how romantic, falling in love over a pan!"
I like the jazzy music on end credits: they should play it more!
Ep. 8 the wimpy FL asks for the ghost girl's help in seducing the chef. So many red flags rising! If she cannot muster up the courage to be more relaxed and brave, it is only cheating and this kind of cheating I hate, i.e. having someone else do your work for you and pretend it was you who did it all! NO NO NO & NOOOOOO!
Do writers & directors really think that women talking like babies are cute and seductive? The ghost is just being so utterly annoying with her cutesy voice and aggressive behaviour. This has not aged well! She can perfectly well stand up and walk but he insists on carrying her?!? Why do these men insist on treating the adult women as small, irresponsible and weak children? That ML is starting seriously to get on my nerves: it must be his caveman side - he likes the weak female more than an adult and competent one! He really needs to shed this macho mentality. He had a crush on the women for such a long time but never dared to say anything: now she's giving him strong signals to come and ask her on a date, he does not want to?!? What a cretin! Men are really afraid of independent women: how much low esteem does he have!
Please, can we get a likeable character in here?
And that ghost in ep 9? She is beyond annoying? Could not the writers find a middle ground where the fls are concerned and not make them complete opposites? And the ml falling for this behaviour: blowing hot and cold, shy and pushy? Did he really fall for someone with apparently split personality or is he just an idiot? My two cents worth of psychology would say he is still deeply insecure about his own qualities, he never managed to completely get rid of low self-esteem which made him a bullying target in his teens. He still seems to be that shy teen hiding not very deep inside the successful adult!
The extremely annoying ghost is still trying to get into the ML's pants, "seducing" him with baby voice and buckling his seat belt: this is the first time I've seen this in an asian drama. Usually it is the opposite: the macho man reaches over to take the girl's seatbelt as if she is not capable to do it herself (or it is the ml who tries to show his caring macho side).
I am watching ep 9 in short instalments: it is so hard to watch to the point of being unwatchable. The FL has definitely better chemistry with Cordon than with the ML.
So she goes drinking with the kitchen staff and ends up falling asleep in a motel room around 2AM. He gets all panicky and goes to get her, sobers her up and then they go home together I guess around 4AM. And his mother visits at that moment?!? Really?!? Ridiculous!
Ep 11 so the ghost is dating the chef and realized she is in love with him. He used to refuse her demands for sleeping together but now that he is ready to go further she is refusing. She'd turned from an aggressive female to a shirking violet, jumping as if electrocuted at the slightest touch! This dynamic is reminding me of Doom At Your Service which was the same: the FL stopped being forward once she fell in love! Another annoying trope!
I am only curious now to find out how the writers are going to sort this love triangle mess. Who is he really in love with the shy girl or the ghost? But by the end of the episode, the girl has realized that the one the chef likes is the ghost not her and told him that! Finally, some honesty! This is getting interesting....By the way, what happened to the nice jazzy music? Now that the things are getting serious, we are on to the soppy pop music?
So right at the moment when I thought they could not go any lower, the sleezy, creepy sous chef interviews candidates for a kitchen aid position. This is the pinnacle of sexism: do you have a boyfriend etc. and then he dismisses a candidate who is married with a kid! Not funny or cute just humiliating.
No, this is definitely not getting any better: just the opposite!
Ep 14 and the "pearls of logic"just keep coming: the ghost girl possessed the shaman lady but she is still incapable of turning pages and looking at her own diary? !? What is the point of possession? Just to talk?
Ep 15 Surprise surprise!!! The bad guy became evil because he was not loved by his parents! Boohoo! Give me a break! You are really going down that path, Writers, poor little unloved boy?!?!? His deeply buried resentment made it easy for the evil spirit to possess him?
And of course, the girl cannot tell the chef the news over the phone, that would be too simple! They need to see each other which will of course give the bad guy enough time to kidnap her or whatever so she would not tell anyone and bring out the ghost girl! I want to drop this so much! The last time a drama annoyed me so much was And I Married My Antifan!
And of course, the bad guy seems dead by the end of the episode! Why would he stay alive and face the consequences of his actions? Too complicated, right? How about he survives but with amnesia?
Finally, the last episode i.e. the wrap up or "they lived happily ever after" and the ghost girl is gone but she left most of her character traits with the other girl who is now cheerful, confident and speaking with the baby voice. At least the brilliant jazzy music is back.
The most repulsive and disgusting character is that sous chef: harassing the people working under him all the time. I don't understand why no one says anything? Still the hierarchy in the korean society? A person older than you is allowed to insult you and harass you as much as they want?