Non-<table> grids and treegrids

I've been thinking about ARIA grids and treegrids more from the point  
of checking them for conformance and, therefore, from the point of  
view of the hoops authors need to jump through.

Writing conformance checker rules that require role=row on <tr> and  
role=gridcell on <td> feel very author-hostile. On top of that,  
there's the issue that <tr> is never really a child of <table> when  
parsed from text/html.

According to the Best Practices draft, using a <table> "in some  
instances that may not work for the developer". What instances are  
those? Considering that released IE versions don't support creating  
CSS tables from <div>s, how common is it really for authors to make a  
treegrid/grid widget out of <div>s?

Does the <div> case *really* need to be supported--particularly at the  
cost of making the <table> case needlessly inconvenient?

-- 
Henri Sivonen
hsivonen@iki.fi
http://hsivonen.iki.fi/