Not been brave enough to test its very low speed capability - it will allegedly stop the the car but I don't fancy having to expain if it doesn't. At higher speeds, it's jumped in a few times when it's seen traffic ahead slowing quicker than I am, knocking off the cruise control and on one occasion, I'm pretty sure it applied the brakes - in every instance its intervention has been justified, though it panics sooner that I do, which might not be a bad thing.
The flashing lights/beeper is a more frequent alert, and it can be fooled by it not being human - as an example, where I live there's always a couple of cars parked on opposite sides of the road causing a chicane as I enter the estate - the system always fires up as I overtake the nearside car and am then seemingly on a collision course with the offside car -I know I'm going to move back over but the system doesn't. It's no big deal and you can reduce the sensitivity, if required.