The for $79.99.

Digit-Life reviews the Creative Xmod in context of using it with notebooks and PCs. They test the signal quality with LynxTWO (details) professional grade sound card. Their verdict is that the Xmod is an interesting device for notebooks, but for the money you could buy a sound card with similar functionality.

CNET reviewed the Creative Xmod with portability in mind. They like the audio quality, but would rather see the Creative X-Fi functionality integrated in mp3 players. The Xmod needs a power supply away from a USB port, which is not included. Nota true portable solution.
More Creative Xmod Reviews:
Generation MP3 (French, the first review)
Laptop Mag

If you know about another interesting Xmod review please email me.