but I have a tendency to believe that if one must have a two-party system (and for some unfathomable reason, apparently we in the US must), the best scenario is when the executive and legislative branches are controlled by the opposing parties. That way neither party gets everything they want and by and large the public is served by their need to compromise to get anything done.
And so true. Here in Australia, for the first time in decades, on the federal level the Government (currently the Liberal party (Australian conservatives) ) will have control in both the Upper and Lower Houses of Parliament (that is, the House of Representatives and the Senate). We don't have an "executive" branch, but the party with the most seats in the lower house is the Government. The leader of that party is the Prime Minister. For the lower house, the person who gets the most votes (done with a cascading style of voting) gets the seat. The Upper house, however, uses a much more complicated proportional representation method. And so it is easier for the "third" parties to get seats.
This means that compromise happens. It has to. To get the laws through, the Government has to either deal with the opposition (which it does a lot more than would be expected) or the third parties who have the balance of power.
But now (or soon) the Government will have a clear majority in the Senate. No compromise is necessary.
We are all screwed.