I went to Nielsen's first example (http://foodnetwork.com) with NoScript enabled (meaning it degraded to CSS-only solution) and it worked quite well.

It was actually quite hard to get diagonal issue to be the problem, you must follow rather unnatural path to get out of the active zone.

And 0.5s delay was detrimental, site felt snappier without it.

I'd think you'd need javascript/flash for that.