Re:How tested is this technology. (Score 2, Informative)

I cannot tell about Japan, but in Zurich (Switzerland) two such plants are operating since 1969 (continously upgraded). A link (in german, unfortunately) to the technical description: http://www.stadt-zuerich.ch/internet/erz/home/khkw /technik.html. The plants do not only generate electricity, but also heat, which in transported to industries and houses in the vicinity (a couple kilometers around the plants).
Most interesting, and answering a lot of the previous question is the PDF about the energy production:

• Electricity production: 91500 MWh
• Internal electricty consumption: 38000 MWh
• Net electricity production: 53500 MWh
• Heat production: 406000 MWh

A second PDF links to the emission statistics. For the non-german speakers: the red bars are the legal limits, which are quite strict compared to the US.