I would also recommend the Tonerider British Distortion - instant Led Zepplin and, with the drive turned low and the volume up, an great fuzz box type sound.
As to their other products - I had a Mule-a-like when I was saving up to put two mules in my Esprit and they were not bad, certainly as good as any mass market after market pickups, but the mule beat it in the end by a long way.