Some people abuse the open PTO policy. I have seen people taking PTO every month and not getting any work done at all, but that is accepted as it's the employee's freedom to decide when and what to work on.
The managers say that it's an open and safe environment, but in reality there is no transparency and no freedom so say what you think. I was told not to point out problems unless I have a solution ready. That is the same as saying "you can't ask questions unless you have the answer." It does not feel like a safe environment when you get criticized for asking questions.
The evaluation system is not very fair, as it gets heavily influenced by the opinion of the managers. Even if the whole team gives you positive feedback, if you don't get along with one manager you will end up with a negative evaluation.
There is a problem with harassment as well. There have been sexual harassment incidents but the company failed to take any action to prevent this kind of problem from happening again. Overall it is not a safe environment to work in, especially if you are a woman.