I really have nothing to add to the commentary on today's party-switcher, Parker Griffith of Alabama, now a Republican. He voted with the Republicans before, so there's no reason to expect his voting pattern to change significantly, although it most likely will change some -- he was the 10th most conservative Democrat this year, at least by one estimate, and all House Republicans are more conservative than the most conservative Democrat. Actually, my guess is that he'll be a mirror Arlen Specter, going from not quite the moderate extreme of one party to safely in the mainstream of the other. The difference is that while the distance traveled may turn out to be similar, the importance of that distance won't be. No one really cares whether Griffith votes with the Democrats or the Republicans on votes where the Dems are united and the GOP splits.
Except, that is, the people who decide on committee and subcommittee leadership roles; moving to the right will give Griffith a shot at a future subcommittee chair (or ranking member). And the people who vote in primaries. It remains to be seen how Griffith is greeted by his district's Republican voters. As it was with NY-23 and as it is in FL-Senate, potential candidates (and party-switchers) will be watching to see just how tolerant GOP primaries are of differences.
Beyond that, it was probably a fluke for the Dems to pick up that seat, and now it's safely back in Republican hands. A nice one-day PR boost for the GOP, and that's about it.