Do Nordost QX4 purifiers worK? Upscale Audio is $1.649 vs. $2,700 so looks like a good buy

What do you think of the Nordost QX4 Power Purifier? What difference(s) did it make to your system?   Were they "big" or "small" differences? Some have complained here that this item is a relatively few electronics in a heavy aluminum box at a crazy high price.  Upscale Audio has them new for $1,649 so that's a +$1,000 saving off $2,700.  Thank you in advance for your candid thoughts - they are much appreciated! :-)