Haven't had much opportunity to play with the new Sigma 120-400 yet but here are a couple of hand held shots at 400mm from Vancouver Harbour. Suddenly several new factors come into play when using a lens with this long of focal length, heat waves and haze especially on the longer shots. The OS (optical stabilization) works far better than I expected. I am able to hand hold a shot at 400mm with 1/30sec shutter speed and get good sharp results.
Will post more pictures and impressions soon as I have time to play with this lens a little more.