The worst is when in traffic and the sun is in front of you,the glare for the driver behind you is intense and they can't see your brakelights at all.
If someone does rear end you with blackouts on the car,and they hurt their neck and such,you're insurance company will not cover you because you're car was illegal.Imagine sitting in the court room getting slammed by the judge,as the medical bills pile up for the other cars passengers.
I love blackouts,but not worth the risk to me..maybe on a garage queen,or for shows,but not a daily driver..jmo.