Since nobody came forth I will try my best to help.
My curriculum is mostly 5 years of game jams, so essentially all I deal with are beta testers. I've never had a game fully released as a product, so feel free to disregard everything I say :) My points are only meant to make games that are fun to play.
I believe in the first place you must be open to criticism, don't act defensively. Try to respond clearly to their doubts and comment on their concerns, but don't say they're wrong or that they don't understand something. Try your best to extract things from the player, not input stuff into them. This is useful because you will not be able to reach every player and input your thoughts into them on launch, so a clean perspective is your best ally, don't tarnish it.
People will often only be able to express personal observations and not necessarily with regards to target audience, industry standards, market placement, etc, so take their insights and thoughts with a grain of salt. They are not speaking THE truth, they're speaking THEIR truth.
Let them speak and take their time, sometimes they just need to vent a little. When you get someone passionate about something, they might be heated. You don't have to listen to s***, but if they keep it respectful, let them have the floor. This experience is also important to them and if they cherish it, you have the start of something great. A game can only benefit from having a healthy relationship with its players, and beta testers are the building blocks of the community.
People will give bad ideas... A lot! They don't know what you know. They don't know the strengths nor the limitations of your TTT (tools, time and team). Always listen, but they are not developing the game. You are. Always be clear about it with them too, you are looking for feedback, not a creative director.
The bad ideas are not a bad thing though. People don't know what you know, but they know what they like, and most important what they dislike. When you hear something that is really off base, take the time to understand why the person said it. What is the essence of the comment? Does the person wants more speed, challenge, options, story?
Lastly, don't worry too much. Respect yourself and your team's vision. Do what is best for the game always, but try to give people space to talk about how they feel about your project, sometimes you'll hear something that makes all the trouble worth it. You'll get a lot of dirt before getting some gold.
Being very specific about data, focus on what strategies emerge from gameplay more than the player from which they emerge from. More important than what people look like or what they say is what people do. If they don't have the tools to do something, consider making the tools, in this way people will be able to communicate to you better without necessarily using words.
Hope this helps a little. Best of luck to you!