When I started to watch this drama, things were going the way it was expected to be. People who often watch kdramas and historical dramas are very used to a certain MO and even script-writers tend to follow the model. '100 Days My Prince' rejects the usual. We are introduced to a peasent world and a peasent's point of view in that time, something very unusual in a historical drama. We get to see the rich, the poor and the rich becoming poor - the last one, very entertaining and funny in a way you can laugh and remember about the scene and continue to think "ah, it was so funny!".
As the title says, the couple stays 100 days married in a village as poor people and the drama takes most of its episodes in that scenario. That's why a lot of people say they don't like the script and they are afraid the plot will be rushed at the end - but if the responsible for this is a good story-teller, you don't need to worry. People say they don't like it because they are afraid and because de M.O is different - it tends to cause a strange feeling to longtime kdrama viewers but I must insist that it has been very good till now.
The actors are very capable, not only the main couple, but also the supporting cast. We don't need the main actors in scene to be entertained and I think this is rare.
In conclusion, is it worth watching it? Yes, of course! It is very cute, but it feels more real too. It is a little bit different and the way the plot resolves itself may feel slow to you who often watches kdramas, but every episode will entertain you and personally this makes me more curious towards the end ;)