Toku's UB
1) 10% late game boost in production is not trivial
2) Toku does NOT need coal at all (assuming you have oil) which means ALOT less unhealthiness during the modern era. IronWorks suffers but the 10% boost of the UB offsets it a bit. It also means he can freely build an industrial Park in all cities with little concern for unhealthiness.
3) IMHO, the Japanese UB is much stronger than it get's credit for.
Ditto.
Aside from some really obvious UB's that border on overpowered (Ikhanda, Terrace, Sacrificial Altar), the Shale Plant is one of my favorite Unique Buildings in the game. The health bonus from not connecting Coal is amazingly good and I've even been lucky enough once or twice to have Coal pop up on a mined hill that didn't happen to have a road, so I got the tile production bonus without having to get the resource.
Yes, cutting yourself off from Coal does make the Iron Works production bonus a bit lower (an extra +60% instead of an extra +100%), but the extra health in the Iron Works city means you can switch a couple of tiles to Workshops or possibly even support a couple of extra population points in the city if your

+

keep you below 20. Those missing

points have made up for the lost production bonus in most cases.
Additionally, the lack of a Coal requirement means that you can build a Shale Plant to provide power in your National Park city. I can't stress enough what a big difference that makes. The National Park city isn't just a big GPP farm, it's also an outstanding city for your choice of Science, Production, Cash or (especially) Espionage. You can run a zillion Engineers in a National Park city when you're building Infrastructure and that extra +50% production bonus is a free

from each of those Engineers. Even without Engineers, you'll end up with enough population in the national Park and enough hammers from specialists in general that an extra +50% production is very nice.
Japan is the only Civ that can have power in the National Park city before Hydro Plants and I have noticed that I often build my National Park city in a way that will allow me to maximize the number of forests and that pushes me onto a city tile that isn't next to a river. No river = no Hydro Plant and I'm not about to build 3 Gorges Dam just to give power to the National Park. Also, I don't often lack Coal across my entire empire, but it has happened. When it does, I yearn for Shale Plants.
Japan is really a quite decent Civ as long as it isn't played by the ridiculous AI.