How many Formula 1 Cars have the new KERS system?

So far Mclaren have it on both cars as do Ferrari and Renault. BMW also have it available to both drivers, Heidfeld has used it in both Melbourne and Sepang, whilst Kubica has yet to use it due to disadvantages it gives heavier drivers such as him, this is due to the weight of the system which ives the heavier drivers hardly any ballast to help the handling of the car. I think Toyota will have there system up in the next race in China which will be good with the ridiculously long back straight at Shanghai. Cant wait to see Williams' alternative flywheel system should be interesting. So far Mclaren probably have the best system which i predicted in a question before the season and got a few thumbs down?