On the other side Sony F828 (more expensive an Z1) at 30fps will "work" only with a specific card.
I read too that with CF type II is working well. I'm using a 256 Mb Viking (write 2.8 Mb) and I get at 30 fps 2'55" max and some delay.
At 15 fps it's difficult to notice it. I made several tests with speaking directly on the front of the camera. If I take a group it's very difficult to notice a delay at any fps.
I'm very sensitive to this problem because I find "unsink" often on movies too.