Briefly, it's evidence that you're
- Capable of writing at a professional level
- Capable of writing within relatively narrow confines (page, already existing history, etc).
For finding collaborators, that's invaluable. An artist who is trying to break in needs a writer who can write at that level, and is serious about putting in the work. Most aren't. Many people want to be a writer; few want to write. Having won the award, there's an assurance that they'll be hitching their wagon to someone reliable (though maybe not to their personal tastes; but at the very least they won't waste their time reading a bunch of mediocre scripts; it will at least be competent).
Immediately I was given 'open ears' to pitch to editors at a couple of mid-level publishing companies; sitting in a bar, one higher up told me "oh yeah, we love Mark, he does the work so we don't have to"
That doesn't mean anyone's going to publish your work. For a while, it basically meant I got an opportunity to get rejected a lot. But that's valuable too -- pushing you in different directions, refining what you do.
I won't go into it specifically, but @Mark_Millar personally took time and effort to look at some of my stuff and help me out -- above and beyond anything promised by winning the contest. He's been an AMAZING supporter. I owe him so much.
I'll have three series announced in 2017, one ongoing and two minis (though there is a chance one of those will be turned into an OGN). They're all collaborations with incredible artists. I can't say anymore, but the feedback I've gotten from some of the biggest people in the industry - editors, artists, writers - has been overwhelmingly positive.
And I owe much of that to winning this thing.
Also, it was nice to have some pocket money, and it's cool that I get to vote in the Harvey Awards, and it helps to say at cons that you've actually published something, and a thousand other small things.
I know a couple of others have gotten deals subsequently (Ricardo, Steve) as well.