The gist is that the govm't wants to take you off of a pension system and put you into a 401K that they control. The money gets dumped into Wall Street and you can lose your shirt if Wall Street does a pump and dump like they did in 2008, but you have no control to get your money the hell out if they wish to do so.
I think the powers that be know how small the money is. They know how little budgetary savings it will actually be. What they want is to get rid of all gv't pensions--they did this with the civilian GS'rs in the mid 80s. The switch is about the privatization tsunami that is killing all of government, good and bad. (Think about the privatization of Walter Reed and how that turned into a giant fiasco. Remember, for the private crony companies to "make" money (siphon taxpayer dollars of the top), they have to take the money intended for actual medical care.)
Someone on Wall Street wants your pension money to play with. Obama is Wall Street's servant. That's what I think is happening.