[etc]

Хм.

var str = "<block><item>1</item><![CDATA[2]]><item>3</item></block>";
var xml = new XML();
xml.ignoreWhite = true;
xml.parseXML(str);

var node = xml.firstChild.firstChild;
while (node) {
	trace("A: "+(node.nodeValue || node.firstChild.nodeValue));
	node = node.nextSibling;
}
i = 0;
while (xml.firstChild.childNodes[i]) {
	node = xml.firstChild.childNodes[i];
	trace("B: "+(node.nodeValue || node.firstChild.nodeValue));
	i++;	
}

А for-таки медленнее.