I have a couple on my commuter bikes. One old aluminium design and one of the newer plastic ones.
Probably easiest for me to list the pros and cons
pros
Very bright.
Never really have to worry about battery life or charging.
Well built quality light.
Cons
Having an extra wire on the bike is a annoying.
Time consuming to move to another bike.
Angle is dependant on mounting position and not adjustable.
Reduces front light battery run time time.
Light stays on when front light is turned off (Very dim but still drawing power)
No flashing option
Although that list seems more negative than positive I really rate the light and would highly recommend one. If you move your lights around bikes often I would look elsewhere but if you leave it permanently on one bike then there is no real negatives to having the wire. I use Velcro straps to hold the wire to the frame which work well and mean removal is easier than with cable ties. My one is probably 6 years old and the other 3 and I have had no problems with either.
Andy