If you guessed Neutral, you win positive feelings from me. Diversity is a value neutral term. It does not imply good or bad, just different. Diversity can be a net positive in certain situations, it can be a net negative in others, but overall, it doesn't automatically imply a better or worse anything. We have become so entranced by the cult of diversity that we automatically assume that more diversity is better.
Frequently while discussing socialism with folks I know the examples of Canada and the Scandinavian countries come up. Not particularly diverse places and one reason why socialism has worked in those places to the extent it has. (Another reason is that the non-diverse population is relatively small). Even there they are starting to feel the adverse effects of years of socialist policies and are starting to backtrack a bit but that's another topic for another day.
Why am I even talking about this? Well a 2007 study found that the more diverse a community, the less societal trust they have, and the less likely they are to vote, volunteer, or engage in charitable giving. Read more at the Boston Globe by following the link above.
For more on Robert Putnam, Harvard professor and the author of the study, here's his Wikipedia entry. He also wrote a book called Bowling Along which you can pick up through Amazon by following the link below. I will be reading it but the pile of books that I have bought and haven't had a chance to read is reaching dangerously high levels and until I can remove some of them, I hate to add to the height of the stack.