I just finished one drama what in mine book is "hidden gem" bc everybody is talking about "Full House" and how cool Rain there is. "Full House" is like pale shadow if compare it to "Sang Doo, Let's Go To School" ( http://mydramalist.com/korean-drama/496/sang-doo-lets-go-to-school ) and how he acts there. I like Rains rolemakeings only in two dramas (this and other is A Love to Kill. Btw both dramas are written by same scriptwriter) where he really gives all what he has.
Other big plus with this drama is - Lee Dong Gun, who makes here one splendid siderole. You can see in this drama how well Rain and LDG can coact and you end up wishing to see them together in some next drama too.
Like i mentioned somewhere already - this drama is like selftest, you get to know are you optimist or pessimist.