This is one of those fuzzy areas. Google claims keyword in domain name is dialed way back, but webmasters still see it creating a strong advantage. The challenge in analyzing this effect is in sorting out the influence of backlinks with the domain name used as anchor text.
My own experience is that keyword in the domain name is only a small help - but it is definitely a real help. Since it's an important keyword, there are bound to be a lot of other relevance signals around that keyword on the pages of the site.
Then there's the user data possibility - keyword in domain name is going to draw user clicks, and that could indirectly help the site rank better, too.