Random observations from a Parisian in Tokyo: I love the sink on top of the toilets way more than the electronics.

I'm not super convinced by the water jet. It can make a mess, it requires a lot of paper to dry if you don't want to wet your pants and if you don't have soap, are you really cleaning?
Heating seat feels like overabundance (a common thing in Japan).
But the sink to clean your hands and reuse this gray water for the next flush is amazing. I think it should be made mandatory in every region with water resources issues. It's still not clear to me, however, if using soap there will cause more maintenance issues or not.