They never had a supermajority under Obama for very long (i.e. filibuster proof - 60 votes to break a filibuster).  By the time President Obama took over the Republicans were contesting the Senate seat of Al Franken (this took about 7 months to solve).  In April Arlen Spector changed parties and became a Democrat.  Franken was finally able to take his seat in July.  In August of that same year Senator Kennedy died.  So officially they only really held a supermajority for about a month (with 60 Democrats - if you consider Arlen Spector as a Democrat).  Hard to get a lot through with the turmoil of the first months of the Obama administration - especially with the economy in freefall.