With most of the results in, the Democrats have taken the House of Representatives and the Senate is still up in the air, 49-49, with two seats (Virginia and Montana) still to be decided. Since the vice-president (Cheney) breaks tie votes in the Senate, the Dems need to win both to gain control.
Fox News took an exit poll, and its analysis of the results show why voters did what they did. Definitely check this link out. I have to admit that the poll makes clear that the election was, at least partially, a referendum on the Bush administration and the Iraq war. I'm not yet prepared to admit defeat, though, because the Republicans are going to score more than 200 representatives (out of 435)--that is, the election wasn't a wipeout--, and we'll still have to wait and see how the Senate comes out.
Important point: The Republican candidates piled up a total percentage of the vote that is considerably higher than any of the five parties in the Catalan election. That is, the word "repudiation," which we are going to hear a lot over the next few days in the local press, doesn't exactly apply.