This is totally amazing. But a key disadvantage that the creator doesn't mention: What happens when the population grows more in one state than another? Do we have to redraw the boundaries every four years to compensate? A great little animation would be to see how these states would have changed in the last 50 or 100 years.
They're advertising it directly on their website, so they must think it's worth it even if it isn't non-negligible.
God forbid anyone offend Edward Tufte. GOD FORBID!