Dennis Littel (NED-13) held the record for a little while with a top speed of +34 knots; he was using an 11m and F2 FX-V. It was later broken by someone using a much smaller sail ...
There's some more discussion about it here:
http://www.carbonsugar.com/technique...our-fw-kit-go/
In the Race Against the Machine video, they are actually on slalom kit. Fairly big slalom boards I imagine, but they wouldn't be going much over 30 knots in that swell.