UK, on the A320. There's a big difference between acting as PM (and I have no qualms about speaking up and potentially annoying someone there, as it's my job), and offering feedback directly on someone's flying technique.
I've only done it once (in fact, after the captain specifically asked for it after a challenging approach), and when it wasn't what he wanted to hear I received a bit of a lecture about how a "bit of experience" didn't make me an expert and the importance of keeping my mouth shut.
So, yeah, I'll continue to use our post-flight reviews to pick holes in my own flying - of which there are many, sadly - but will not offer feedback otherwise.