Very nice, light is pretty even, easy to install (although instructions would have been nice, ended up screwing in to the opposite side of fan (e.g. inside the case toward back of case), and screwing the fan in from outside back to case toward inside case. This does mean you can't use the pull through rubber anti-vibration mounts though.
The Halos look great even with dark fans because the light they emit is quite bright. They are easy to install and the come with the screws to attach the Halo to the fan by itself or with a fan plus a radiator.