The rolling shutter disappears a lot in 1080p 60p !
But a bit less sharp as seen here http://www.eoshd.com/content/13116/slashcam-test-reveals-sony-a7s-108060p-softer-24p-mode
According to Philip Bloom comment in his blog post about the A7S, 1080p 60p still looks gorgeous.
Can't wait to see his review !