I've been using a Magnic Light as the rear light for many years now and have never had a problem with it. As a front light though it never seemed to be bright enough. As a rear people have commented on how visible it is so I guess it is. I never actually rode behind it. My front light on that bike is one of the brighter B&M CYO lights with a Shimano 3N72 dynohub. It's been a while since I checked into these thing as I retired 5 years ago and hardly use it at night anymore except the occasional fun ride. I ride well lit streets in NYC so I never really need it to light the road, just to be seen. But when I have taken it on a truly dark trail I'm always very impressed by how much light there is.