So I nerded out while bored at work and made a spreadsheet. In the optimistic scenario, you invest $75 and get paid back $200 within 3 years. It works out to a nearly 50% annualized return. In the worst case scenario, you invest $75 and get paid back $200 within 20 years. That works out roughly to a 2.5% annualized return.
There are two major variables in play: How much revenue the company generates, and how much gets invested. 5% of revenue goes into the payment pool annually, but the more invested the smaller each investor's share. So an investor should hope the company only meets their minimum funding goal and get nothing more.
With such a wild variance I can't see putting anything other than play money into this. As I said, I might kick in $75 to get my $25 bonus and just see what happens, but there's no way I'd put any serious money into this.