Very reminiscent of the work Stamen is doing; I'm a big fan of both.

Here's Stamen's watercolor map: http://maps.stamen.com/watercolor/#12/37.7706/-122.3782

Gorgeous, but painfully slow to render. The price we pay!

Wow! This is absolutely beautiful.

I thought this was going to be the Bing napkin sketch style for directions:

http://infosthetics.com/archives/2010/06/bing_destination_ma...

Love the end result of the bezier curves shown on the map of the Caribbean, but really thought the napkin sketch feature was fantastic for directions.

As one of the comments at your link shows, this was originally developed at Stanford:

http://graphics.stanford.edu/papers/routemaps/

I prefer the traditional style maps because if you deviate from the expected route you still have a map of the area.

For example a GPS device will give sometimes give you a ridiculous number of turn by turn directions in a row. Go 100 feet merge right, go 200 feet merge left, go 50 feet and take a right, go 300 feet and make a left.

There's something very pleasing about dedicating so much technical attention to something that is so artful. I love seeing map styles like this- not sure where I'd use one myself, but I sure want to...

Tangentially related, I like this really simple experiment with map simplification from a few years ago: http://adamsmith.as/blurry_maps/

Obviously not nearly as involved as this, but a nice example of what a really simple transform can do aesthetically: It just median-filters Google Maps, which has the effect of removing text, simplifying boundaries, and producing large flat color areas.

I love that slippy maps are a commodity such that people can making art and craft them in new and wonderful ways.

There's already a nice collection of other twists on the slippy-map-as-art thing here. One more is Stamen's Pretty Maps, which does the heavy lifting in SVG and combines Flickr shapefiles in very interesting way: http://prettymaps.stamen.com/

This is so beautiful.