Well, this comes along at a really good time for me. I'm about to redesign a fairly large site and wanted to at least give a nod to handhelds. Overall the recommendation is very general of course, but it's good to have some direction.
I know some savvy mobile webmasters who can do just about anything they want on the 'Net with a handheld, but as for the general population it's a mystery to me. The very few handheld requests I can track back make it appear that people are searching for very specific pieces of information, though that might change as these devices get more powerful -- and hopefully easier to use.