Quickie: I have the 55-200mm. My birthday is coming up and I'm considering the 18-200mm (Nikon). Good next step up or totally unnecessary?

FWIW, I'm very pleased with the quality of pics I get from my current lens as I have finally "figured it out" well enough to satisfy me. What do you think? And if the 18-200mm isn't a good step up, what do you suggest?