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We had a good experience with BackerClub but I suggest haggling a little bit on their upfront fee. We were able to negotiate a percentage based commission instead.

I had an overall positive experience on Backerclub.
I paid $349 for the promotion package and received €163 on pledges from 3 backers. Backerclub refunded the difference!
I am not sure if my project was a good match for Backerclub and I must also confess that we contacted Backerclub a bit towards the end of the campaign.