I could not agree more with Duncan Black's statement from his Eschaton blog:

As I've written before, Democrats will regret embracing the expansion of executive power because a President Obama will find his administration undone by an "abuse of power" scandal. All of those powers which were necessary to prevent the instant destruction of the country will instantly become impeachable offenses. If you can't imagine how such a pivot can take place then you haven't been paying attention.

There is nothing that has changed with the right wing leaning judiciary when Mr. Bush leaves office.  Those right wing judges on the federal bench will be then willing to hamstring and actively pursue lawsuits against President Obama and his administration.

Remember that the oldest Supreme Court judges are liberal.  If he has to replace judges then President Obama will merely be replacing the liberal wing of the Supreme Court.

With the tools of facism still on the table, due in part to the active complicity of the Democratic Congressional leadership, there will be the temptation to use those powers.  Need I state those tools?  Unitary Executive theory.  Commander-in-Chief powers, the use of "executive privilege", executive "signing statements", USA PATRIOT Act, Protect America Act, AUMF, MCA, etc.

Remember that Gandolf when offered the Ring of Power by Frodo said "No! The ring would be too great a temptation.  The temptation to use it would be through Gandalf's good intentions which would lead to corruption.   (It would take a George Washington strength of character to resist such temptation.)