Dark colored carpet is horrible to keep clean; much worse than lighter carpet actually. I spent many long hours one time looking for just the right carpet to go with my decor and ended up settling on a beautiful dark drown with flecks of rust. I swore, Never again. Especially with pets. It accentuates cat hair.
It looks like my post wasn't clear - we're not replacing the carpet with carpet - we're putting in hardwood floors. I'll have dust bunnies and wads of cat hair swirling around - I'll have to be using a dust mop and my vacuum cleaner often.