Everytime I have told my T when I think he has screwed up, for things that are or aren't his fault, he has always been enormously receptive, even when I haven't said it in the Best Possible Way. He has always said, thanks for the feedback and, more generally, he says he is always willing to hear what I have to say. He even acts like he means it.

Even if indelicate in presentation, I do think T's are especially grateful when you tell them what doesn't work for you, because this is information that makes it easier for them to help you. And I think they are very glad that you can stand up for yourself with them; it equalizes the relationship.