A few thoughts in no particular order:
Not once has an OCer ever said after a police encounter, "I am so glad I didn't have a recorder."
One of the OCers involved in the Tony's Incident privately kicked himself for leaving his recorder at home that evening. The police were able to deny everything the OCers complained happened inside and outside the restaurant. The police couldn't evade the in-car text messages and department e-mails obtained by FOIA, which really showed their anti-self-defense attitudes; but the nastier stuff, like the illegal seizure of seven OCers, that happened at the restaurant was all denied.
Police can screw up even a consensual encounter, giving false information about the law, exaggerating things, revealing anti-rights attitudes. Even if they don't do anything strictly illegal, they can say the darnedest things sometimes.
Its really hard for a bad cop or a borderline cop to lie his way through an internal affairs investigation if there is a recording. Neither can police supervisors dummy up and assert a cop did everything properly when there is a recording.
The bottom line is that while things are generally better than they were five years ago, its not like every cop obeys the law and scrupulously observes rights. Also, things didn't get better for OCers because police decided, "Oh, my. Look at the nice citizens exercising their rights. We should support that." Uh-uh. No. Things got better because we came out swinging on rights violations. And, part of that was having recordings to prove the cops were ignoring the law, twisting the law, and violating rights.