In all the articles I've read it's pitched as being used for addresses outside the "traditional postal addressing" system, in the developing world, where mail gets sent to "the third house on the right after the blue one by the gas station" or whatever. I would contend that " #3J" is a perfectly reasonable address for an apartment in a tower block.

I started to write that if it's being used for post, not GPS navigation, it's also reasonable for a university campus, because you don't address letters to "Unseen University", you address them to a single person, office, or building there... which needs it own address. But then I realized, how many universities don't have a traditional street address in the first place? W3W's sole redeeming use case, as far as I can figure, is for places whose central government can't or won't set up an authoritative naming scheme, or whose layout just doesn't lend itself to such.

Also, re Maidenhead, look at the use case again -- if you're trying to come up with a system that suits the developing world's postal system, hopefully anybody can remember words (especially if using a localized version in a language they speak), but your average bloke in an off-grid tin shack is not necessarily going to know that his address is always letter-letter-number-number-etc. To be fair, I guess it would catch on pretty quickly, but it's still not nearly as memorable as the three-word thing.