OP : yes, the actors have great chemistry (I think they're the best of the bunch amongst the main cast, imho). The way Jessica reacted when she realised he was going to die shows how much he had grown on her. I alternate the whole series thinking : I want them to be BFF. No, I want them to be a couple. No, I want them to be BFF and a couple. No, they're like brother and sister, that's not right. No, they're absolutely not. etc.

Be it as a couple or as very good friends I love that between them there's a nice balance of similarities,that let them empatize with the other, and differences, that add spices and could let them learn something from one another.