There are probably HID kits that 'stray all over the place', but from my experience the kits supplied my BikeGear give a very sharp definitive beam, the end and beginning of the beam is very sharp and defined, there are no stray beams that I've seen.
Oncoming vehicles probably flash guys with HID lights because of the brightness of the light, I've parked my car (BMW fitted with BikeGear HID lights) next to another car that as factory equiped HID lights (Mercedes Benz) and see no difference in intensity. they are both very bright. What makes a difference though is the HID is a very close simulation of actual daylight, so a person's eyes readjust very quickly after the car/bike has passed.
The normal Halogen globe tends to leave a 'residual' after the car/bike has passed, in other words the human eye takes longer to readjust with Halogen lights.
I recommend that if you fit HID lights to your bike, adjust the headlight down a little.
I have HID lights on my 1150 GSA, KTM and my car, and very seldom get flashed.
Before you fit HID lights to a car or bike, first mark on the garage door or a wall where your Halogen lights shine, then after the HID's have been fitted, check them again, making sure the bike/car is in exactly the same position as before, and check them again, often you will have to adjust them down slightly.
As a matter of interest, mark the outline of the Halogen beam, then compare to the HID beam, there should be no difference. You will also notice a much sharper definition.