He was one of the finest actors of his generation with a promise of greatness that mirrored, if not surpassed, James Dean's. I am reminded of a quote by Robert Graves, who said of Shakespeare: "Despite the fact that everyone says he's very good; he really is very good." So was Ledger. He will be missed.
Jim Emerson's touching tribute can be accessed here: http://blogs.suntimes.com/scanners/2008/01/heath_ledger_19792008.html