I'm on a game with Japan, reaching industrial, wanted to remember the good old times on vanilla with Japan.
The culture bonus is nice, you can get it pretty early, is when it matters the most. Later can add a bit extra tourist, something is not bad.
The bonus is modest but, they still retain bushido, and synergyzes quite well in an aggressive approach.
The Samurai boat build is quite original. On the first place I built most of my cities with sea access but by the time I got samurais I only used the ability three times, and because I'm going wide.
I guess the best chance to get the most of it is when a barb ship or an enemy fleet kills your fishing boats, to quickly rebuild them. I don't know if it works for offshore platforms, I'll test it when time comes.
All in all I think this get Japan in an upper tier, but far from the best civs, like Poland, Korea, Arabia and Babylon. Good enough I must say.