As a project creator, BackersHub was one of the few marketing initiatives that was a positive ROI for us.
They have a highly targeted mailing list of people who support multiple Kickstarter campaigns.
Our project is here:
www.satchel-page.com/kickstarterWhile their list is quality and targeted, if your product doesn't convert on Kickstarter or on your website, it won't convert through BackersHub email list. Meaning, if your project didn't make it's funding goal, it's not because of BackersHub's email list or if BackersHub made a typo, it's because you don't have a strong enough product.
As a project backer, I enjoy BackersHub because it shows me quality campaigns that I would have otherwise missed. There is becoming more and more junk on Kickstarter and BackersHub helps me weed through it.