I have just received a 42.5mm f/1.2 from Panasonic UK to evaluate. My goodness it's huge - it's physically larger and heavier than the m.Zuiko 75mm f/1.8, which is already a hefty beast. And compared to the m.Zuiko 45mm f/1.8 - it's almost 3 times as heavy. That's the cost of being one and a third stops brighter.
But that heft is reassuring in a way and of course this lens promises hugely in terms of optical performance.
Can't wait to post some shots