Anandtech has posted their review of the MPX chipset for dual Athlon Bliss. They also said they noticed no USB problems.
Although we've seen reports contrary to this, we noticed no USB 1.1 compatibility problems with the reference Paulaner board. Using the only two ports available on the board we captured video from an Intel USB web camera while constantly using a Microsoft USB Intellimouse without any compatibility issues. While this is clearly not exhaustive testing, we thought it was worth mentioning.