OMO! I recently finished watching Iljimae and I absolutely fell in love with it!
I mean, I liked Lee Joon Ki before, but after Iljimae I have no doubt about his acting skills. And as for the ending, I liked it even though some people didn't. I decided to stay optimistic about it. It could be a good or bad ending depending on how you want to see it.
Other than that, the acting was great by everyone, the writing was amazing, music very fitting, camera work and everything. There was the perfect mixture of tears, laughter, and romance.
Plus I'm a sucker for the superhero storyline. Definitely a must-watch imo. :D