twooffour said:

All of 3P0's emotional reactions seem to be a bit distant and imitated, if you look closely.

He doesn't really mind telling the stormtroopers that the others went to the prison section (I think?); he kinda accepts serving under Jabba; he readily accepts "new masters" as soon as he's sold to someone else; he doesn't come off as terribly despaired after getting blown apart, and yes, he doesn't seem to be awfully sad about Han, either.
With all that, he obviously shows a lot of personality that could be described as annoyed, concerned, afraid, grumpy, self-centered, compliant, etc.

I agree with 2/4 about C-3PO. Throughout the movies his emotional reactions and observations are not entirely normal (in a human sense). That's the character. All the way from "the damage doesn't look as bad from out here" and on.

As far as telling the stormtroopers about the prison section, that was a clearly a ruse since 3PO already knew the stormtropers knew where Luke was and was pretending to be an imperial droid. But the basic point holds.

I really can't think of any line that bothers me much. Strikes me as odd when Luke calls the droids "robots" but not such a big deal. Little weird when Leia is talking to Wicket/herself saying, "trouble is I don't know where here is" but I don't mind that moment overall. Even the bad flirting lines in the OT work because they don't take themselves that seriously.