I guess it's cathartic to vent, but I have to say my doubles got a lot better when I realized I could only control what I did. It's pointless to allow yourself to become annoyed or distracted during a match by what your partner does. Let's face it, you aren't that much better, or you wouldn't be playing with them.
It's poisonous to a team if one member takes on the role of on-court coach or critic, unless they are clearly a full level or more better, and even then, the less said, the better. It's particularly offensive if one member starts eye rolling or sighing or worse after their partner misses easy shots. I just watched the Wimbledon doubles semi's with the Bryan borthers and you know what? Both teams missed their share of relatively easy shots, yet I saw nothing but positive encouragement. That's what leads to winning, not fault finding.