I had one fly open in flight. Latch failed. We were in clouds on a student training flight, and I had to monitor the student, hold the window, and think about the approach. And I have a hard time doing only one thing at a time. Cold, and wet. Bubble windows, 180.
On the other hand, I decided to do an entire flight with the Decathlon window open. Never tried it at full power before, but with Covid, I figured ventilation was better than good hinges. Did fine. No symptoms yet - we both wore masks.