Kidd is actually a decent character and, from what I can tell, has been as fleshed out about as well as Law. Law was designed to be 'cool' and admittedly he is, but that doesn't mean that he is well developed as a character in and of itself. The most Law ever did was save Luffy from the war but we never actually got a reason why. In this he remains enigmatic and not a fully fledged character yet; we don't really know his goals and what he's willing to do to get them.
Kidd is the step between Luffy and Blackbeard. He is powerful and willed and wants to be the Pirate King. Whereas Luffy is generally altruistic and Blackbeard is selfish and prone to betrayal to further his own needs, Kidd lands smack in the middle; he chose to fight alongside Luffy and Law on Saobody archipelago when he didn't need to but also goes around killing any one that mocks his aspirations. He was designed to be that intermediate rival to Luffy, both in terms of Kidd's power and Killer's status as powerful first mate to Zoro. He stormed into the New World rash and eager just like Luffy and caused havoc just like Luffy is. I would say he is not any flavor of the month and is, in my mind, a little more unique than Law is right now (Law being designed solely to be cool and suave and make fanboys drool and, so far, not much else).