I've had these installed in my SEX and Crack amps for months, and for the money, they are great! Channel balance is of course improved, and the notched action is pretty smooth, though the scale appears to be different than the stock pots (in that more of the control is allocated to the lower end of the gain curve, and they get loud pretty quickly after that). In terms of sound, there was a very pronounced "veil lifting," so much so that my former preferences for tube combos in my Crack had to be revisited. I think the attentuators made as much of a difference in sound as changing the output capacitors, which is totally opposite of what I was expecting.
The $12 "DACT style" deals are a bit finicky to install, as they are much shorter and smaller than the stock pots, and there are no solder tabs, just holes and solder pads on the little PCBs. This meant that I had to put some electrical tape on the plate immediately underneath the attentuators, to avoid the solder joints from shorting to the chassis. If you can live with the compromises, these are very nice for such little dough.
EDIT: Also forgot to mention that the secondary hole for the "key" that prevents the pot from rotating when the dial is turned is not compatible with the stock hole on the SEX/Crack plate. A tiny hole must therefore be drilled in the plate, somewhere between the two pre-drilled holes for the stock pot, in order to use the cheap DACT ripoff attenuators.