With halfway decent power stabilization, and the appropriate about of directionality in the lights, plus the lights being somewhere below the typical sedans window frame, the only time headlights should bother you, is when you're on a hill, regardless if they're LED or not.
IMO, one of two things is very wrong if you're getting blinded by anyone's headlights (highbeams not withstanding): either the designers and engineers that worked on the car are idiots, and placed headlights in a location that was going to blind people, or they used crap optics, etc.... Or, the owner of the car can't be arsed to have their headlights properly adjusted.
Honestly, it's a little of A and a little of B... Depending on the car and the circumstance.
One the person I knew actually had self adjusting headlights, which somehow were damaged and would not adjust properly anymore. They drove around like that for years before retiring the vehicle.
Can't fix stupid.
If they flicker it's because the designers/engineers did something wrong. It's an entirely DC system, so the only way they would flicker it's if they're using PWM control for the intensity of the lights. There are better ways to dim LEDs, which don't introduce flicker.