This is an interesting data viewer. It's nice to have a quad-viewer to compare different point densities like the the attached below for the Portland area. I think it's interesting to note that the viewer and data are from a grant under the Models of Infectious Disease Agent Study that's used to study the dynamics of infectious disease transmission!
I also think it's interesting to look at the different color choices they made for the different categories as well as those from other recent dot density maps (hey, I thought light blue indicated the white race?).