From a developer standpoint, Idealist is certainly different. I saw a project that I liked on Idealist called PrintPass where the user had agreed to back the project with cash, and I decided to join it for the 20% equity stake that he offered. Because I had to sign an NDA to see the project I can't really say what it's all about, but I can say that I'm able to build it, and when it's done it will be great. I feel like I'm a part of the project- a cofounder- but not an employee.
So, does this new model work? Well, if you're looking for employment or some short-term cash, Idealist won't deliver that. But if you're looking for your next big project then Idealist is the only way that I've seen to guarantee yourself a committed business partner to collaborate on a solid project.