I am using the .22 uf CuTF as coupling caps in my BAT 150SE amps. They replaced the TFTF caps which themselves were a big improvement over the stock caps. Now in comparison, the TFTF caps seem more clinical compared to the CuTF caps. The highs are smoother, the midrange fuller and more lush, and the overall sound is more involving and musical. The best of a copper PIO combined with the best of teflon.
New V-CAP CuTF capacitor
V-CAP has just released a new capacitor - CuTF - copper foil/teflon that they feel is the cat's meow. Apparently a lot of R&D went into it, per their website. It is more expensive than the TFTF but appears to promise the "soul of music" inherent in copper. I've been quite happy with the TFTF (tinfoil/teflon) caps I put in my BAT VK150SE amps but have decided to take the plunge with this new cap. Will post results in the near future.