I would never use a hyphenated domain name!
First off, they do not qualify for the exact match bonus, which typically renders them useless when it comes to seo benefits. Second, a lot of people neglect to enter in hyphens when referencing a domain name... so if you own Green-Dress.com, you're going to lose traffic to GreenDress.com, I guarantee it.
For file names, hyphens are great - they are interpreted as spaces.
For domain names, hyphens are not good at all, and I would stay away from them.
No. HireSEO.com would rank for the term 'Hire SEO' before hire-seo.com would, simply due to the exact match domain name bonus.I have another site hire-seo.com again this site took just a few weeks to get to page 1 for the search term "hire seo" so I have to wonder if the same taking longer thing would have applied it the doman name would have been hireseo.com.