I found Love in the Mask while I was searching for good gender benders to read, and I absolutely loved the premise. The story kept me hooked until about chapter 80. At that point I started to dislike where the story was going so I dropped it (plus the male lead's undying devotion was getting on my nerves). When I saw that it had been completely scanlated, I decided to give the ending a shot. I read it from the beginning (skimming through a few parts), and forced myself to keep reading until the end.
I really didn't like the last 30 chapters or so. They were fine to read, but I felt as if the story I'd fallen in love with had disappeared. I would have been much more satisfied if the story had ended around the time when the main characters finished high school. It felt like I was reading the ending from a distance because, for some weird reason, I didn't have any emotional connection to the characters. I didn't absolutely hate the ending, but it wasn't done the way I was hoping for (which can be a good thing in some cases, the ending being a suprise and all, but I felt really let down by the whole setup).
Another thing that really bothers me is that the revelation of Hyun Bin's gender seemed very... anticlimactic. I love gender benders and always hope that the main character's true gender won't be revealed too early on, so I was glad that Hyun Bin's disguise lasted for a while. But then it kept dragging and dragging and, when it all came down to it, with the hypnosis and the forgetting and everything, the "big reveal" just wasn't satisfying at all. And am I the only one who didn't like the long-haired guy (I think his name was something Bi-Rak... it's been a while)? He was really annoying and I think the story would have been a lot better (and shorter) if he was completely taken out of it. I hated how his presence distracted from the main couple at the end.
The art (especially facial expressions) was never spectacular, but it really started to bother me about 2/3 of the way through. I think I wouldn't have minded the story's shortcomings quite as much if the art was better.
All of that said, I would be lying if I claimed that I hate this manhwa. I really liked the beginning, was disenchanted by the middle, and was pretty disappointed by the ending, but I'm still glad I read it. It's not the end of the world if you end up not liking it, so don't be afraid to give it a shot if it seems interesting to you.