Obviously, what a Dem House means right now is a rebuke to the Bush White House.
The cable commentators have been talking about whether the House will be more conservative, since liberal Republicans are losing and many of the new Democrats are relatively conservative. I'm skeptical on this point. Remember that it's not just a GOP talking point that incoming Speaker Nancy Pelosi and future committee chairman Barney Frank, John Conyers and Charlie Rangel are all quite liberal. That's who'll be setting the agenda, not the few more border state moderates.
The GOP's strategy in recent years has been to use the iron control of the House floor to push through legislation that Bush has wanted, using their 9-4 Rules Committee advantage to block most Democratic amendments. House passage of Bush priorities has forced Senate votes on many priority issues for the GOP. That dynamic now is done.
One curious difference this all could make is that a Democratic House might pass a more liberal, or certainly less punitive, immigration bill -- of the sort that both President Bush and the Senate have already signaled they would favor.