I picked this show up because I fell in love with Jang Geun-Suk in You're Beautiful and Marry Me, Mary! I'm not a fan of his short hair style but his cuteness comes out in spurts throughout this drama. Although he plays a 2nd lead he turned his character into an admirable person.
Beethoven Virus didn't have the strongest start. It took me until episode 3 to really grasp what happened in the first two. Kang Gun Woo Sr. is a trip! You'll love to hate him. His performance is what kept me watching through some of the weaker episodes. As we near the half way point the story picks up the pace and you really start to feel the characters love for music and their devotion to the pieces they play.
Other than the slow starting pace, the only gripe I have is that I didn't find Rumi appealing as a lead female (greatly outshined by secondary actresses by the way), Her character's personality and situation was almost pointless. All it did was enhance the performances of the lead males. If she weren't in the show at all, the drama wouldn't suffer.
This isn't one of those cutesy-poo romantic comedy Kdramas. This one maintains a serious tone. There's lots of side-story telling full of close-to-home style tension involved with the other characters. In the end I was left smiling and satisfied with the result.