How to change the logo text.
   

This feature will only work if you have a valid license key

To customize the logo string you will have to use two property entries. In the first one named "logoString" you can place the string you want to display. But this will only work if you place the license key in the "licenseKey" entry. Here's a simple sample: 
  Properties props = new Properties();
  props.put("logoString", "my company"); 
  props.put("licenseKey", "INSERT YOUR LICENSE KEY HERE");
  AeroLookAndFeel.setCurrentTheme(props);
  UIManager.setLookAndFeel("com.jtattoo.plaf.aero.AeroLookAndFeel");

See also:

How to change the theme.
How to use a predefined theme.