I am still using OTA throughout the system. The only exception is with the power cables. I went back from OTA PCs to NBS Statement PCs. But I have not yet tried the larger .65 mm OTA in this application.
Regarding using other cables with OTA. I could only really bear using the NBS PCs with OTA, whereas the NBS ICs and speaker cables, when added, colored things in the NBS direction (darker, slower, more rounded) very quickly, so that the OTA effect was lost altogether.
Since I last posted, I replaced the wire inside my speakers (a larger-gauge solid-core copper wire from Britain) with OTA, and separated the crossovers from the speaker cabinet. The results were entirely positive. I threw out the old cable without a second thought. I highly recommend wiring the insides of the speaker with OTA if you decide to use it as a speaker cable. If you leave the manufacturer's interior cable inside the speaker, the full OTA effect will not be achieved.
I have also used OTA as a DC hook-up wire. I even direct-wired parts of my amps and crossovers with it, which is a real challenge, because of the small diameter. The results were well worth the hassle.
Recently I was talking to a dealer here in Europe about his experiences with other solid-core copper cables (DNM, Audio Note, etc.), and he said that whenever he used such a cable, the sound just seemed to explode with life from the speakers. While he was saying this, he made a gesture with his hands like a supernova. I liked the metaphor. I will loan him some OTA soon for his store set-up.