Why is there a big bump in election analysis now? Because states generally release results by county, and it's taken this long to go through the precinct results and break things out by congressional district.
The latest CQ crosstab sort of the data is by physical size of congressional district, and there's a strong correlation: the smaller the space, the better for Obama, and for House Democrats. Republicans like to brag about the seeming redness of the map, but as we'll see a lot of that red is the more cows than humans turf of the Great Plains.
The full chart is here (pdf).
In Iowa, we have some relatively large districts; in fact, Loebsack's 2 and Latham's split-ticket 4 are near the top size for Obama districts. (The chart's not numbered, but Loebsack is on page 9 of an 10 1/2 page list, while Latham and King are on page 10.) So by national standards, we're few and far between out here.