They come in a rainbow of colors (as well as many patterns), but there's also functionality behind this simple and attractive mug.
The ceramic used by Waechtersbach is lighter than most, and it gives the mug a very pleasant weight. Other mugs seem like boat anchors by comparison. It is slightly more fragile than harder ceramics but well worth it due to the wonderful feel in hand. Heck, I've probably saved $30 in food cost over my lifetime due to consuming fewer calories by lifting this lighter mug :).
Also, if you brew with a Melitta drip coffee maker (#2 cone), you can fill it exactly twice and it comes up to about 1/4" to 1/2" below the top. Perfect; no overflow (test this; your mileage may vary).
You can purchase it on the Waechtersbach site for $10.00* or at various department stores. I bought some recently from Foster's in Philadelphia via their web site for $8.00*. They shipped within a day and were very well packed, arriving in perfect condition.
* as of 10/17/2008