>This version assumed I'd use two consecutive for-each clauses, one 
>for the B children and one for not-B-children.

>So we'd be talking about a select="not(B)" here, wouldn't we?

>When I try this though:

><xsl:foreach select="not(B)">
>    some diagnostic output here
>    <xsl:apply-templates />
></xsl:foreach>

Yes, you and David Carlisle are right. 
not() is an expression and you must have a path

<xsl:foreach select="*[not(self::B)]">

Cheers,

Juergen

 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list