I tested the Sony EX1 at various settings including its overcranking setting. Clearly the best setting for slow motion is 720 30p with S&Q at 60.
Make sure you're in 30p because when I shot the 60p footage I was wondering why it wouldn't work when I dropped it in the timeline.
(If you do shoot 60p, there is a way to convert it to play back slow forums.creativecow.net/thread/142/860140)
I had thought I read something that you can only shoot 60 fps for about 3 seconds, but clearly that is not true.