Arrow's biggest failing was their Laurel casting. When Amell has scenes with her that look and feel like these two people just hate to be with one another and we're supposed to buy that they are the OTP, its a fail. On top of that, when you see Amell with everyone else and they have chemistry (I mean, you have people buying in on Thea/Oliver to Digg/Oliver to Quentin/Oliver for God's sake), you just have to shake your head and sigh that they screwed up so badly with the only relationship that IS canon and the 'core' relationship of the show.

But then when you introduce a character like Felicity that immediately is the opposite of the behavior and attitude of your 'lead actress' and works SO much better with your lead, you are asking for trouble...