This being really my first lens, I've heard some bad reviews of it and I'm hoping someone can chime in here and tell me why this is not a great lens. I like it for its overall range, its versatility but I realize its not the ideal lens for any given situation (except for travel, which I do a lot of).

But I do find that some of my pictures just turn out awful, especially shots of people, colours not coming out very well, or quite dark. I do consider myself a novice still, despite some very decent shots that I've learned to take, so it could be operator error, but I'm hoping to get some info on why this lens isn't very good, and what you recommend.

I notice that Don has recommended the TAMRON 18-250, or its predecessor, 18-200. I'm very interested in a straight 90 or 100mm macro, and wondering what to look for in a lens.