I bought this pedal for my Peavey Vypyr VIP 2 amp. It is pretty much essential since, without it, you can't use the amp's built in looping function. In addition, the convenience of having control of the amp at your feet rather than having to fiddle with buttons and knobs on the amp makes it a worthwhile purchase.
The only drawback is the price... a bit expensive, I think, and the Sanpera II even more so. I also wonder how long the cable connecting the pedal to the amp will last - it's quite a heavy, multi-wire cable and could prove to be a problem in the future... only time will tell.
Overall: an essential purchase if you have the matching amp