Terri, I've heard they do lay alot of eggs but they don't go broody.
Blue colored Runners lay blue eggs too!
The black might too.
I'm sure they will help control your bugs.
I noticed after getting Muscovies how well the keep the flies and mosquitoes down.
If you get some I recommend Dave Holderread in Oregon.
He has very good quality.
Much better than hatchery stock.
http://www.holderreadfarm.com/
I'm going to get his deluxe variety Runners next year
whick includes some rare colors.
Alan...follow your impulses!