Well we can thank the computer industry for the fact that they exist at all. Unfortunately there is a decreasing demand for through hole parts, while Murata makes this type of cap they do not produce a leaded part. So far only Nichicon, Panasonic, United Chemicon, and Rubycon make large numbers of through hole parts that are readily available in the U.S..
What's killing us here is the form factor chosen by all of the manufacturers of capacitors utilizing this technology and of course they are building for a specific market. We are not even on the radar for the type of audio applications that this technology is suitable for.
I use these caps for coupling line level single ended class A output stages. As long as you don't have too much DC offset these beat any other technology you could apply. They are also stunningly good when used as a DC blocking capacitor in a power amplifiers feedback loop. You could also use them on the nose of the amp to close the door on DC. The thing that will dis-qualify them from some coupling applications is their high leakage current compared to other electrolytic cap technologies. The gone and much lamented Rubycon Blackgate caps just did not have any leakage current to speak of.
DoS communicated the concept poorly in his initial comment. What he was referring to was the trace layout on his circuit board which requires the caps polarity to alternate in order to stuff them in the holes without shorting them out. This alternation of the positive and negative traces reduces the overall inductance of the traces and reduces the tendency of the capacitor bank to ring under high current loads.
Obviously you can't just stick the capacitors in the board anyway you want just to reverse their polarity.
Scotty