I wrote an interactive QtPy program- it receives video frames over the net and allows the user to interact (steering a microscope) in real time. I use millisecond timers (which generate signals delivered to slots) all the time.

After doing a bit of tuning I was able to steer the microscope with no visible latency, which means I'm handling user events at ~25FPS or higher and not seeing any high variances. The only problems I have are when the handler that receives a signal takes longer than I have budgeted (IE, more than 1000/25).