Still, multiprocessing objects like Array and Manager are limited to ctypes.
Sometimes worth it, but often not. The ability to do shared-memory multi-threading is one of the things that tempts me away from Python. Message passing is great and all, but sometimes you want your messages to be passing around control of a shared 4GB data structure, instead of trying to copy it.
A little hacky, yes, but extremely effective. I wrote an image processing application for somewhat large time-series datasets (> 1TB) on Linux which took liberal advantage of these details to run very nicely on v2 Xeon processors. It also worked quite well for GUIs which interacted with the datasets.