Looking into the parallella, looks interesting but the main processor is "just" a dual core and then it has this :
"The unique Epiphany co-processor chips consists of a scalable array of simple RISC processors programmable in bare metal C/C++ or in a parallel programming frameworks like OpenCL, MPI, and OpenMP. The mesh of independent cores are connected together with a fast on chip network within a distributed shared memory architecture.
I'm not sure how many programs in linux out of the box are going to be utilising these extra cores. There's also no spec given in that description for those processors. I'm sure if you're working on parallel processing projects it's gonna be useful but for someone like me the benefit is gonna be little to none. Maybe even detrimental as the benefit of the Pi is that so many projects are being tailored specifically for the Pi, resulting in more help online, more base images to start from and more compatibility with projects in general.
Still, a cool idea and shows how many kickstarter style projects there are that I am completely unaware of!