I have 2x E-M1 and I fixed on 12-40 and 35-100 f2.8 respectively. I find that the balance with 12-40 is really bad, such that I have to use a battery grip with it. I bought the grip for use with 35-100, but now I need to use it with 12-40 instead. Think whether to buy another grip but will be waste of money and additional weight. I will lose out a L-Fn button and the working distance for close-up shot, if I switch to Panasonic 12-35 f2.8. Dilemma.