These lights are a fantastic piece of kit. Replacing a 4 year old Cateye LED Opticube light the power difference is incredible and having USB recharge and long battery life are a definite plus. The narrow profile doesn't take much handlebar space and the main beam pattern is almost square so the light can be set to avoid dazzling oncoming drivers and cyclists. It's very well constructed with a metal case, good sealing on the USB port and a screw in battery. The shape is also suited to taking it off the bike and using it as a torch.
Generally, I use this on hyper constant mode which works both for lit city streets at night and as a daytime 'running light' making you more noticeable in the same way modern cars have additional LED lighting. Its a constant low beam (which is still brighter than my last light) which regularly pulses to high power. This gives you enough light to see and be seen from a considerable distance away. The only minor complaint would be that there is very little side lighting even with the cutouts so I also use a Moon Comet light which has 180 degree visibility but doesn't light the road as much. I've taken this on a few unlit trails which is good for getting home on reasonable paths and if supplemented by a helmet light works well even off road.