Without anyone getting kicked in the face…

You always need to listen when people don’t like something. You are too close to the game; You probably already fixed all the things you didn’t like, so you should value a fresh perspective. Keep in mind that you can always trust someone’s emotional reactions, they are always authentic and valuable, but never just blindly take their advice. The designer’s job is to separate emotional feedback from thoughtful suggestions and treat the appropriately.

Before you can interpret someone’s feedback, you need to understand the source. Feedback means “the game in my head is different” and often times your response to feedback should be to probe about what kind of game they are imagining. You don’t necessarily need to agree on the game you are making to benefit from their feedback; they probably represent some portion of your audience.

You see Development Bias a lot with the public when the development process is very open. Playtesters know the game isn’t finished, they know you expect them to provide constructive criticism, so they become a lot more sensitive and more likely to complain. Once the game is on the shelves, those small problems fade into the background and players rarely notice them.

You also need to understand the source of feedback; If you can categorize someone’s play style, it will help you understand how to react to their feedback. You can weight their comments appropriately.
Here are some examples:
(The names have been changed to protect the guilty)

I used to balance “Easy” by playing with my nose (true story) but Steve still couldn’t beat it. I miss that guy, he was incredibly useful for balancing.

Even more important than categorizing other players, you need to understand your own playstyle. For instance, I’m a “role-player”, so I tend to ignore small balance problems if the results are still dramatic. I have to recruit “pros” that are more sensitive to useless or underpowered elements.