More gridlock. Seriously. It's not like much is getting past the 60-vote requirement in the Senate, and the House and Senate aren't going to agree on anything huge anyway.
The biggest actual change probably surrounds confirmation of presidential nominees. But at this point, 1/3rd of all federal judges have been nominated by Obama, so that doesn't hurt as much as one would think. The vacancy rate is relatively low at this point since Obama and Reid have prioritized filling-in empty seats.
It also changes the expectations game of the Republican base. They're going to expect legislative results now that their party controls all of Congress. If Congress gets no mileage towards their goals (however unrealistic those goals may be), the base might get upset, which could trickle over into 2016 turnout. If the GOP reps over-reach and threaten to shut-down government if Obama vetoes their pet bill(s), the blowback from the voting public could be very fun to watch.
It also finally gives Democrats ammunition going into 2016. Get used to hearing "the Republican Congress" from various Dems running for office two years from now. Bill and Hillary have experience in successfully using a Republican Congress as a political scapegoat/foil.