I won't read the comments above, they're full of spoilers and i'm only at episode 6 :D
I actually started watching this drama when it first started airing, then after 3 episode , i became really busy and out of my 4 currently airing dramas (Bride mask, I do, I do, Mirrai Nikki and Big) i had to keep only one and it was The Bride mask : tough choice yeah but i end up postponing it not "on hold", just postponing, now, i'm able to watch it again, i have to say that this is getting really interesting.
So far, i love Gong Yoo, he's an awesome actor, i just made sure now then there's Lee Min Jung whom i always like her as an actress.
Speaking about characters i hate Lee Se Young because she have the typical korean second lead female common and boring character and i really like Ma Ri.
One more thing i should mention, i really dislike old-young relationships specially if it's the girl who's older but i guess this can be considered as an exception.