This is a toilet I recently used at the fish market in Hachinohe.
The first thing you'll probably notice is the water basin on the top. When you flush the spigot releases water for you to wash your hands right there, and the water fills the tank to be used for the next flush! Saves a lot of water if people use it properly!
Next is of course the heated seat. I will admit, they are pretty awesome! I have even heard that some places have fans or A/C for hot days too!
Bidets/washlets (the one above has a washlet) are very common in Japan also. Most of the washlets shoot a stream of water to clean your behind, and then some have an air dryer to finish the job and dry you off! I haven't experimented with that yet.
During our in processing they told us that some of the toilets can have a control panel with as many as 40 buttons for all the features. This toilet had a control panel with about 5. The biggest problem is that they are all in Kanji so good luck guessing!
Probably one of the most interesting things they have in the bathroom is something called an otohime (directly translates as "sound (oto) princess (hime)). Apparently many Japanese were shy about the noises they made in the bathroom so they would constantly flush the toilet so no one else would hear them. To combat this huge waste of water the government created a public campaign to educate people not do it. This apparently didn't work but the Gucci of toilets, Toto, created the otohime. It's basically just a little box that either plays a recording of flushing, some music, or some other masking sound.
So now you know more about toilets in Japan then you might want to know!