I have no illusions about being able to keep a nation state attacker off my devices, but not having all of my correspondence shared with all kinds of third parties by default sure feels nice.

Don't forget anonymity with temporary/throwaway devices and handles combined with E2EE PFS protocols can be very powerful to thwart such surveillance.

Except that if your target finds out, it would undoubtedly increase their paranoia level, making future attacks against him harder and compromising future operations. There's a reason why law enforcement keeps wiretap warrants sealed.