I live in Tokyo and I think it's great. You can often see people at McDonalds early in the morning after a night out catching a nap before the trains start running. Just buy a coffee or something, grab a table, take an hour nap -- great. And this is Japan so you don't have to worry about your stuff getting stolen! Even if you sleep at the train station!

I also commonly see people taking naps during lunchtime in Starbucks. Someone will come in, grab a coffee, take a nap for 30 min, drink the coffee and go back to work. There's nothing wrong with that! (other than I want the table :P)

Unfortunately the corporate culture is not where it should be. There are some companies that want to be like western startups where taking a nap on the office sofa wouldn't raise an eyebrow but those are very rare. In most Japanese companies it would be totally unacceptable to sleep in the office.