It's cool...if you need to demo lots and lots of caps, especially for customers...but I've gotten the same effect with a couple of wired alligator clips. No "knob" to turn, but it takes 2 secs to switch caps.
I recently did some cap comparisons, as I added small toggle tone cap switches to a few of my guitars. They are separate form the caps that are tied to the tone knobs. It lets me shave some highs with a flip of the switch. They are much smaller caps - picofards - I use a 320 pF and a 560 pF.
One is dialed in for the neck PU and the other for the bridge. They are tied directly to the signal, not the tone knobs.
I still have the tone knobs with their caps, but I rarely use them. The toggle is quicker and it's just the right amount.
