gistfile1.js

  list: SC.ScrollView.design({
      layout:{width:250},
      contentView: SC.ListView.design({
        contentBinding:"Accounting.invoicesController.arrangedObjects",
        selectionBinding:"Accounting.invoicesController.selection",
        rowHeight:70,
        exampleView:SC.View.design(SC.Control, SC.ContentDisplay, {
          contentDisplayProperties:"contact".w(),
          classNames:"invoice-item",
          render:function (ctx) {
            var c = this.get('content');
            if(!c) return;
            ctx.addClass('status_'+c.get('paymentStatus'));
            ctx.push('<label class="number">',
                      c.get('number'),
                     '</label>',
                     '<label class="total">CHF ',
                      Accounting.formatCurrency(c.get('totalWithTax')),
                     '</label>',
                     '<label class="contact">',
                      c.getPath('contact.fullName'),
                     '</label>',
                     '<label class="sentDate">',
                      Accounting.formatDate(c.get('sentDate')),
                     '</label>');
          }
        })
      })
    })

What I think i would do is:

contentPropertiesDidChange: function(){
  this.displayDidChange();
}.observes('*content.contact.fullName', ...)

and then remove your displayProperties stuff