Use title instead of nid for node reference contextual filter
The reason Views' user reference field allows both the user uid and name is most probably because they are both unique, while the title of a node isn't guaranteed to be so, but of course the nid is.

If, however, your content titles are unique, you might try using it as the contextual filter, hooking it up with a relationship (or rather whatever the D7 term is for it :) to the node reference field, and using all of the lower case transforms and spaces to dashes stuff.

That only leaves a problem if the title has funky characters in it, eg, if the title is This &amp; That your path has to be pagename/this-&amp;-that for the view to work which is ugly to say the least.

Now, how I've dealt with this is to create another text field in my content types that I want to search for by title and I store a url safe title in there.  I auto fill them here in D6 land like this:

function MYMODULE_nodeapi(&amp;$node, $op, $a3 = NULL, $a4 = NULL) {

  if (isset($node-&gt;field_url_safe_title) &amp;&amp; $op == 'presave') {
    module_load_include('inc', 'pathauto');
    $node-&gt;field_url_safe_title[0]['value']=pathauto_cleanstring($node-&gt;title);
  }

  // all the other nodeapi stuff here

}


and now I can use pagename/this-that by filtering on this field instead of the title.

I use the nodeformcols module to hide this field on the node edit/add forms and don't display it in the node itself, but I am sure there are D7 ways of doing that.  Obviously, in D7, I'd also assume you'd use hook_node_presave() instead of hook_nodeapi() and add in a language array field when setting the field, but the logic would remain the same.