I think Rory is good. He is there for a specific reason, and is portraying it perfectly. The point is, no one could have stood against the adventures the doctor can take Amy on, and we didn't want another Dr/assistant love story, but we did want a foxy red head in short skirts. So, they have to combat that in the story, now, as I stated above, irrelevant of character, no one could be interesting when compared to the doctor, therefore the only way to combat that is to have a "true love story" where she chooses the person she loves, irrelevant of their flaws, over the adventures the doctor can take her on. Now, you can't have it both ways, you either get the sassy Amy who is willing to stand up to the doctor and choose the path of true love, or you can have a soppy Rose-esque story line. as we are bored of the latter, we want the former, that requires background and cohesion, Rory provides that.