Four LEDs should be rather bright, and this should be a great light for being seen. But there's a 'should' here already that points you towards the fact that it's not as good as it could be. The unit has constant, flashing and sequential flashing (one at a time in turn) modes. The problem is that the LEDs are recessed quite far back into the reflector, and this means that the light isn't as good as it could be from the side. It doesn't kick out enough light to ride with down a dark country lane, but considering the size of the thing (small) and the fact that it's powered by three AAA batteries, it doesn't do too bad a job.
The mounting is a simple split-band with rubber inserts to allow fitting on standard or oversize bars, and the light unit itself simply clips in and out of the mounting. It feels insecure, but no amount of should-be-illegal bicycle abuse could make it break free from the mount.