Ok, since I had time today and nothing better to do I decided to see which camera/lens combination is best for portraits. I took the GRD II with 40mm lens, GX200 and LC1 which were both set at 50mm to give a comparable result. The 'I, Robot' head was around 30cm away from the cameras. All cameras were shot wide open so the GRD II at f2.4, GX200 at f3.5 and LC1 at f2.1.
Unsurprisingly, the LC1 gives the most pleasing bokeh and has a shallower DOF than the Ricoh cameras due to it's larger sensor, also the 28mm lens is not really suited for this and gives a big DOF. What was surprising though is that there is hardly any difference between the GRD II at f2.4 and GX200 at f3.5 and both look very similar, I had expected the GX200 to have a bigger DOF.