Since when is ALA publishing articles with non-valid examples? DOCTYPE anyone ? Apart from last example, rest of them look like ‘94.
Second, final example - the one that actually demonstrates the article’s essence in all browsers - fails in IE as submenu is offset to the right. Is this just me, as I don’t see it mentioned in the article. I tried refreshing and all kind of things, but it simply does not work.
Third, that final examples is image based. I, for one, expected to see all-text example, where the real challenge lies. Images are easy, since one does not have to worry about resizing problem nor about correct positioning of the submenu so that hovering down is possible.
Forth, this very topic was tackled over 1.5 years ago, when Alex Robinson did first tests about it and asked  (few times) on css-discuss list for help on sorting out few issues. I took the plunge and we came up with solid solution , that works nice with ems (resizing problem that is mentioned in comments). I tested it with real-life example, and it worked, more or less.  If I remember correctly, I think that I sent a message to css-discuss about it.
Few months ago I perfected that example thus it works just fine now, in all I could test with (IE, Opera, FF, Safari). 
Thus we have over-a-year old technique featured in ALA, which used to publish really ground-breaking stuff. Sad. And who knows what other goodies are buried in css-discuss archives…