Also, these distributed processing platforms are extraordinarily leaky (for anything non-trivial, you really need to have a good low-level understanding of your

Also, these distributed processing platforms are extraordinarily leaky (for anything non-trivial, you really need to have a good low-level understanding of your system in order to tune/debug/optimize/implement). There are definitely other benefits of a unified API, but making it seamless to switch underlying implementations is probably not one...