A glance at the World Trade Center site from Greenwich Street tells a lot about progress there: Eight years after the Twin Towers fell, a 10-foot-tall, barbed-wire fence still surrounds the 16-acre void in the heart of Lower Manhattan.  Squabbles over designs and funding have caused severe construction delays. With the exception of the SOM-designed 7 WTC, a 52-story tower completed in 2006...more.