I did some brief testing with the E-M5 and Panasonic 100-300mm lens today. All testing was done at 300mm. My hands aren't the steadiest, YMMV, but here's what I found: At 1/80s, I was generally unable to get a shot completely free of handshake blur regardless of the settings I used. I could almost always get a decent shot (no horrendous blur), but at 100% view there was almost always some handshake evident. At 1/160s, nearly all my shots were free of evident motion blur whether I used the OIS, IBIS (IS 1), or both at the same time. Neither OIS nor IBIS seemed superior to the other. Both OIS and IBIS do a great job of stabilizing the viewfinder, with OIS doing slightly better in this regard. Results were comparable for video, but again I thought OIS was slightly better for this. Overall I found little to no difference in efficacy between body and lens IS. The most surprising thing to me was that leaving both systems on at the same time didn't produce any problematic results (other than probably faster battery drain).