Yes, most of the ebb and flow of good and bad news for the president is massively overblown. Health care isn't going to fail because Obama loses three news cycles.
However, there is one area where relatively short-term trends, such as last week's bad news for the White House or this week's good news, can really make a large difference. Right now, potential candidates for Congress are assessing the political mood. Their decisions -- specifically, the decisions of strong potential candidates -- will probably be far more important to the outcomes of the 2010 elections than will the actual conditions of November 2010. So it certainly behooves Republicans to try to convince everyone that Obama is Clinton '93 Redux, and for Democrats to spin hard the other way.
Because if "everyone knows" that 2010 looks like a good year from Republicans, then all the good GOP candidates who stayed put in their state senate seats (or whatever) in 2006 and 2004 are going to give it a go next year. If "everyone knows" that the Republican party is a hopeless rump filled with crazy birthers and other lost causers, those strong candidates will wait. (And vice versa on the Dem side). So when you're wondering what all the fuss about the Town Halls is about, well, that's a part of it.