I started a site ten years ago with a hyphen in the domain.  The domain without the hyphen was owned by a domainer.  The harder I worked the more traffic he received when my customers typed the domain without the hyphen.

I finally paid a lot of money to get the domain without the hyphen.

On another project I had a domain with a hyphen.  Within a year I was able to obtain the domain without the hyphen in an auction.  When I redirected the hyphen domain to the non-hyphen domain the rankings went up immediately.   Immediately.