A lot of time the lens is poor thing, always get the blame for unsatisfactory photos. The quality of photos many times are due to the user. IF you can have people taking great shots with kit lens, I don't see why there is a need to think that, okay my shots are bad so i'm gonna get a 17-55 to replace my kit lens. The 18-200 is a pretty good lens, and its especially useful when u travel, where u can go both wide and long while not needing to change lens which can be really troublesome. I believe there quite a number of people who likes the 18-200 alot.
A lot of times, the quality depends on how you compose, how u expose your shots and also whether u focus correctly. You can have a shot of a person, then you don't focus your subject, go and focus on something else, say a banner. Of course, it will be not satisfactory.
A "better" lens don't make you look more pro, or take better pictures.