Yep, you can implement your calculations as shaders, which I bet is really useful for matrix multiplication and doing stuff in parallel. That and better graphics performance.
For example, you can't match the performance of this Game of Life implementation with Canvas2d. http://glslsandbox.com/e#207.3
I just have to ask if someone knows: Is there any benefit to doing this in WebGL? Does that enable you to use the GPU for other calculations than the graphical ones? (I really don't know anything about GPUs, so sorry if that's a naive question).