I've used a capsule hotel in Tallinn.
The problem with capsule hotels is that it attracts the wrong crowd. In Japan it works because they are considerate.
I've used a capsule pod for a week. Drunk people having sex above your head is not fun. Those plastic pods are a bit flimsy.
The last day there was a whole polish work crew that invited there girlfriends. They had no problem walking around in their underwear.
I had this Japanese vibe in mind, but that was quickly gone.