I would really like to know this too.
If you look at the help file:
(I hope that's a functional URL) It says that the old drag-zoom thing should still work. But I still get the "scrub" style zooming. None of the pref settings seem to affect it. Help!
In cs5 with the zoom tool selected, uncheck the box in the
tool options bar: Scrubby Zoom.
A big thanks!