I use the underground frequently. It doesn't really feel like half of it is covered. Where it is available, it works amazingly. I might have been using the other half by sheer luck.
I’m not sure about the privacy implications of this whole setup. It’s basically turned the underground into a surveillance dragnet that can hoover up all sorts of interesting metadata… hostnames, hardware identifiers, traveling patterns, DNS queries, SNI requests… and an untold amount of unencrypted communications across weird protocols and devices..