Now this is great little test! One Canon EOS 5D Mark II and one Canon EOS 7D mounted on the same tripod filming at the same time gives you a great comparison of the rolling shutter effect.
Rolling shutter @ identical panning speed: Canon 7D vs Canon 5D mark II from Mike Kobal on Vimeo.
this is an update to my first test, a bit more conclusive.
please check my blog for a few more discoveries during this test, download the 720p versions from here.
There's a bit more to read over on Mike's blog
(Photo credit: snap from the video)