This discussion occurs regularly and is almost always polarising. I have a slightly different take on things ....
If you're upgrading a cheap, unspectacular guitar on the cheap, it's probably not worth investing $10-20 for a tone cap that may not make any audible difference to your ears. However, once someone is looking at upgrading a good guitar with expensive pickups, it's usually logical to make sure that the pots and wiring are also up to a good standard, so one might then spend more on new pots, wiring harness, switches etc. After all, if you invest in $200-300 pickups, it would be silly to compromise them by using poor quality pots, switches and wiring, surely ?
At that point, it's not a big deal to invest in a very good tone cap, so that regardless of what the conventional wisdom may be, and regardless of what you think you hear, you know you've installed the best cap along with the best pots, switches, wiring and pickups.
All my guitars have Sprague Vitamin Q caps. Can i hear the difference ? I don't know, the caps were installed at times when the guitars got new pickups and improved electronics. But i sleep fine at night knowing my guitars have the best parts in them, no compromises have been made, they sound brilliant and there is no need for further consideration; now i can simply play them.
And considering each guitar probably had $300+ spent on upgrades, $10 for a tone cap is a very small percentage of the total, so in my mind, the bad decision would have been to NOT upgrade the cap.
No doubt most people will not agree with my approach and would prefer to continue debating the issue. Personally i think it's worth $10 to just move beyond that and get back to playing.
For those who'd prefer to continue debating, just get some Wima red-box caps. Cheap and virtually boutique.