I haven't written a review in a while so take what I say with a grain of salt. I truly believe Black Knight deserve one to serve as a buffer of sort to all the negatives comments in the comments sections.  
I have been watching dramas for over a decade now and I can fairly say that Black Knight is one of those Love it or Hate it drama. Personally I like it, it  wasn't spectacular enough to take me to the love level but it was warm enough to bring me to like.
So if you find yourself  looking for a drama were you know that there is 99% of chance that the plot and story progression will go nowhere, then you have found yourself at the right stop. Because that is exactly what you will get plotwise here :" NOWHWERE". But don't let the nowhereness of the plot deter you from 20 hours of free cheese and well place laughter if you know how to turn off your overthinking cap.
Let's  give props where there are due.
Go into this drama with zero expectations of wow moments and you will be the happiest person on earth. Go into this drama with a mind set that is ready to jump at every plot whole and expecting (a+b)=c moment and you are going to be the most miserable person on earth.

I came into this drama for Kim Rae Won and I was not disappointed, he showed that yes he is a veteran actor and he can work with whatever is thrown at him. And let's thanks this drama for giving female viewers out there a somewhat healthy male model,  Soo Hoo was kind, hard working and mature. He acted like a gentleman from the moment we met him and showed us that it is possible to want to attain childish dream while being an adult about it.  Something that we have to admit K-drama don't always show us.  So if you want to just chill and watched KRW do his thing then watch this.  

Jang Mi Hee another veteran actress also shined in the mastery of her craft. She portray reformer Baek Hee with class.  Making us laugh at her eccentricity at the right moment and cheering for her to attain the absolution she so wanted. Go in at least just to check in Beak Hee moments even if you have to skip through the drama.

Seo Ji Hye  truly surprised me with her portrayal of Sharon. I'm not going to be singing her acting prowess because to me she more of  a hit or miss actress. But  I have to say that she nailed Sharon essence.  If what we wanted from Sharon was a emotion spot holder than an actress with better control of her facial expressions and mastery of acting would have been better.  But for what the drama came to give us of Sharon SJH  was a good choice.  She has that entitled feel to her.   If you have to check this out well at least check some of Sharon clip, she was at least funny in her eccentricity. Yet also delivered the right amount at annoyance at the mastery of the lack of development her character went through ( which I personally  think was intentional.) It occurred to me that maybe the point that the writer was trying to make with Sharon lay in her lack of moral or personal growth.
 
Acting wise these three are the only one that stood out for me. While it was quite cute watching Shin Se Kyung and Kim Rae Won be cheesy and cute together. Shin Se Kyung once again failed to invest me in her character, she seemed to be a simple place holder around which everyone else gravitated in order to be positioned right.  
  Reading this I can see yourself asking what I'm trying to get at and what the point of these long review that doesn't really say much.  Well I what I truly want to say is, ignore the nagging people and the eternal discontent. Grab a bag of popcorn on a rainy and watch this, even as a place holder to cure that itch that you have for waiting for the other drama that you really wanna watch.  It would not be a wasted 20 hours.  It would just be  20 hours that you spent enjoying some nice cinematography, you will have some decent music and some visually attractive people to watch for about 20 hours.  Then you will move on with your life.

Don't come in with expectations and enjoy the laugh and MOST OF ALL: DON'T OVERTHINK THINGS.