Looks like the 5D mk II isn’t immune to the skew produced by a rolling shutter, although it performs better than the D90 for sure — and I’m sure a careful shooter can produce some very impressive footage with either one. Although you mainly notice it in the video above when abnormal shaking movements are made, that kind of issue can really mess with the natural look of a medium-speed pan — say, tracking a car passing the camera.
Another problem occurs in flickery light, for instance some fluorescents, which may be lighter or darker in certain parts of the frame due to interference between the light’s “frequency” and the camera’s electronic shutter speed. Oh well, the camera’s still sweet as hell. [Thanks for the tip, Mike, and tell me if I'm getting it wrong]