It would not do to embrace the data as definitive. As the post notes, samples for some states are fairly small. (Here's the fun techy details for those who want the story behind the pretty maps.) Still, it challenges the conventional image of socially conservative poor folks voting for tax cuts for the rich because Baby Jesus cries for every abortion. It suggests that critical influences on Republican v. Democratic success in the Presidential election depended heavily on socio-economic class rather than "culture war," with voter participation from key socio-economic factors as determinative.
While it does not include information for '00 and '04, it would be interesting to see if the income correlation holds, and if states that flipped from R to D in 2008 also had a significant shift to voter turnout by poor and middle class voters (either because poor voters became more engaged (especially if one also factors in race), or because the number of poor voters increased). If the correlation is born out, it would suggest the need for significant strategy shifts in 2010 and 2012.