jenk

It's not just that it makes it harder to pass laws (altho, let's face it, the harder it is to pass the more likely the trivial will die in committee). It saves us money. From The Economist:

Between 1995 and 2000, with a Republican Congress acting as a check on a Democratic president (and vice versa), real federal spending per head remained nearly frozen. When Mr Bush took office, however, Republican lawmakers were reluctant to restrain their own man. In Mr Bush's first five years real per head federal spending grew by 3.1% annually, making him the most fritter-happy president since Lyndon Johnson (see table). Under Mr Clinton, the number of federal employees shrank by 200,000 (excluding the armed forces and postal service). Under Mr Bush, it rose by 79,000.

William Niskanen, a former economic adviser to Ronald Reagan, speculates that divided government itself may be the key to fiscal restraint. Using data going back to Harry Truman's time, he found that real annual growth per head in federal spending averaged 1% under divided government and five times that under unified government.

Divide and save
Annual growth in federal spending per head under recent administrations

Unified government* Growth,%

   Lyndon Johnson (1963-1968) 4.6

   George W Bush (2000- ) 3.1^

   Jimmy Carter (1976-1980) 2.9

Divided government Growth, %

   Richard Nixon / Gerald Ford (1968 - 1976) 1.9

   Ronald Reagan (1980-1988) 1.7

   George HW Bush (1988-1992) 0.6

   Bill Clinton (1992-2000) 0.3

*President's party controlled House and Senate during most of term.
^First five years.

Source: "Buck Wild: How Republicans Broke the Bank and Became the Party of Big Government", by Steven Slivinski.

Granted it's only 40 years of data, but it's pretty interesting.