dynamic.html

  <dom-module id="my-table">
    <template>

      <!--iron-list items="[[items]]" as="item">
        <template>
          <div>
            Name: [[item.name.first]]
          </div>
        </template>
      </iron-list--> <!-- this will re-render correctly when items are added -->

      <iron-data-table items="[[items]]">
        <data-table-column name="First Name" sort-by="name.first">
          <template>[[ item.name.first ]]</template>
        </data-table-column>
        <data-table-column name="Last Name" sort-by="name.last">
          <template>[[ item.name.last ]]</template>
        </data-table-column>
        <data-table-column name="Title" sort-by="name.title">
          <template>[[ item.name.title ]]</template>
        </data-table-column>
      </iron-data-table>

    </template>
    </dom-module>
    <my-table></my-table>

dynamic.js

    Polymer({
        is: 'my-table',
        observers: [
            'usersAddedOrRemoved(items.splices)'
        ],
        properties: {
            items: {type:Array,
                    value:[],
                    notify:true}
        },
        usersAddedOrRemoved: function(splices) {
            console.log('users added or removed',splices)
        },
        addUser: function(user) {
            this.push('items', user)
        },
        ready: function() {
            console.log('my-table ready')
            this.addUser({name:{first:"bob",last:"smith",title:'mr'}})
            this.addUser({name:{first:"dan",last:"smith",title:'mr'}})
        }
    })