Milliways is basically exactly what it looks like, I'm afraid I don't have a lot of extra insight here. It's a world, but of a unique kind (Downside is also an unusual kind, but it behaves more like a regular world than Milliways does). Milliways is kind of the Joker of world "niceness". It'll be nice or terrible according to inscrutable whim. It can be relied upon in certain ways, except when it can't. I don't have anything else at this time, although a detailed inspection of the place is on my long-term to-do list.