How to replace the Secondary menu title with the current Username?
I think you can simply do this by making change in page.tpl.php file.

Just replace,

'text' =&gt; t('Secondary menu'),


with,

'text' =&gt; t($user-&gt;name),


save and clear cache.

Image-1: Before changing code (I have deleted line 'class' =&gt; array('element-invisible'), so text can be visible)



Image-2: After change,



Final code,

&lt;?php if ($secondary_menu): ?&gt;
      &lt;div id="secondary-menu" class="navigation"&gt;
        &lt;?php print theme('links__system_secondary_menu', array(
          'links' =&gt; $secondary_menu,
          'attributes' =&gt; array(
            'id' =&gt; 'secondary-menu-links',
            'class' =&gt; array('links', 'inline', 'clearfix'),
          ),
          'heading' =&gt; array(
            //'text' =&gt; t('Secondary menu'),
            'text' =&gt; t($user-&gt;name),
            'level' =&gt; 'h2',
            //'class' =&gt; array('element-invisible'),
          ),
        )); ?&gt;
      &lt;/div&gt; &lt;!-- /#secondary-menu --&gt;
    &lt;?php endif; ?&gt;