It does show the the difference in areas where Kerry won. I does not show clearly enough the difference between Bush and Kerry.
Using PA for an example, it shows 392,000 more votes for Kerry in Phila than Bush received. It doesn't show how how many more votes for Bush there were in the "T" region of PA (this excludes southwestern PA and the suburban Phila counties). If that number is less than 392,000, then the map is good. Bush, however, did get more than 392,000 from that region.
This show that Kerry had support in many large cities; that is hardly news. What is important in PA, for example, is that Kerry won the Republican counties bordering Phila. The map doesn't show that too well.
I kinda agree with J.J. Having said that it is WAY better than those red and blue maps by county which show EVEN less information. I guess that maps are a poor way to look at an election. Tables and charts etc. do a better job.