Spoilers alert:
Loved; the action, seriously the opening episode is explosive but the fight choreography all the way through was excellent and I loved how it used Dal Geon's background as a stunt man to make the action more interesting.
Loved; the chemistry of the leads but also the fact that the story didn't focus on romance. So many 'action' dramas turn into never ending 'will they won't they' mushy love-fests, this doesn't and it's better for it.
Loved; the constant revelations, cliff hangers and double crosses. Makes for very exciting viewing. Have to say the 'ultimate baddy' is not hard to guess as they are hiding in plain sight but getting to that reveal was hella fun.
Loved; the badass women. Instead of watching love sick women get bossed about by men it was great to see the women (whether good or bad) be victorious in the face of doubters or just being super villains.
Disliked: I'd like to say nothing, but I can't decide if I loved the ending or need more. My main complaint about most non k-dramas is that they go on for 5 years and the story never really gets resolved...so if it ends here I will be happy and still give 10/10 but I would watch a hypothetical season 2 in a heartbeat.
Neutral comment: I know ALL dramas have product placement but it was particularly un- subtle in this, not that it affects me really...anyway, I'm off to get a Subway wearing my Lancôme lipstick.