I bought this compressor ten days ago. Since then, I have tested it with guitars equipped with single coils pickups and humbucker too.
With the humbuckers I felt this effect to be very soft, and I thought it can be non-functional. In contrary, the effect is working very well with the single coils. Therefore, I can say that, in my case, the humbuckers (Gibson Classic 57) were already compressed by nature, and the effect is not useful, and barely audible.
With Fender Texas Special single coils, the compressor works well, without "colouring" the sound, but only affecting the dynamics of the signal. With a tube amplifier, the effect push harder the pre-amp, giving more clarity on clean channel and a little more distortion on the dirt channel. I can't comment the quality respect to other brands, since it is my first compressor.
Given the price, I can recommend buying it.