I was not keen on watching this drama but the pretty gifs on tumblr made me do it. The first few episodes were a task to get through but once it picks pace, it is amazing and a very enjoyable drama.
However, if you're looking for some girl power moments or solid teamwork sort of a thing, you are going to be disappointed because Vincenzo does ALL the work and also takes ALL the credit, it gets really frustrating at times.
The acting performance by all the cast members is absolutely phenomenal, they carried the show on their back. Especially Ok Taecyeon and Kwak Dong yeon. Song Joong Ki is breath-taking as always, this time with his visuals AND his performance. Jeon Yeobin was great too, though I would have loved to see her kick some butts in the court :(

Conclusion: Vincenzo is a must-watch for the outstanding work of the actors. The story crumbles in the last few episodes and the whole deal becomes quite violent for no significant reason. If that's your cup of tea, you can go ahead with it.