well the grain at 400 is the same as if you were to use 400 and up speed film. I don't know why they'd continue the trend. Seeing how it's digital I don't see why it should be grainy because there's no film emulsion to deal with.
I usually leave my camera on 200 ISO, but the 400 comes in handy in bad lighting conditions.
Have fun playing with your new camera Marko
