No personal experience (thankfully). But one of my former staff used one of these pods for a very short time in Helsinki en route to France late last year. She said it was uncomfortable (mainly being enclosed I think) but no problems with cleanliness or general amenity. I suspect that's because no-one was really using them for sleep - people were seeing them as a novelty.
I think I would get claustrophobic quickly especially if the air-supply to them is fiddled with?
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