Last year the "deadline" for notification was April 1st, and sometime around April 5th the website finally posted that there was a delay until May 30th ... even so, I didn't get a rejection letter until mid-June. There is a reason they include the "schedule may be changed without notification" clause. Based on the banter from 2010, there were some delays that year as well.
"If selected to receive a fellowship, you will be contacted no later than May 1, 2012 and should subsequently receive your official notification of award by July 31, 2012, for the fall term. Please note that this schedule may be changed without notification due to factors that were not anticipated at the time of announcement. The earliest anticipated start date for these awards is September 1, 2012." (http://www.epa.gov/ncer/rfa/2012/2012_star_gradfellow.html)
ps- F2, Mountain West, still no word.