Part One -
First impressions and light patterns
The Sigma Lightster is a potentially significant new option in battery powered commuter bike lights. Generally, commuter lights are used "to be seen" or "to see". A "to be seen" light is the kind of light you can use in a city where streetlights and other ambient lights provide enough light to ride by. It keeps you from becoming a "bike ninja" by making you more visible. Since the "to be seen" light is mostly used to get you noticed by others, it can be a one bulb blinky or a small light.
If you ride unlit roads, a blinky won't cut it. You need a light that you can actually use to see where you are going.
The Lightster is advertised as a "to see" light. It retails for about $35.00. What makes it potentially significant is that it is a shaped light. A shaped light is a light that projects a square or rectangle of light instead of a circle. A shaped light has a distinct top line. Like car headlights on low beam, the light is focused on the ground and not into the eyes of oncoming traffic. For the rider, it means that more of the light is used on the road ahead instead of fading off into the distance. This feature means that this light is one of the few battery powered lights that meets German standards for bike lights. Even more importantly, the Lightster is the ONLY shaped light I am aware of that sells for less than $40.00. Other shaped lights cost far more.
The Lightster is also advertised as putting out 20 lux of light for 10 hours. A lux is a measure of light. I understand one lux to be about as bright as the light from a full moon. (if that's not right, feel free to comment) By comparison, the Ixon, which is a very good battery powered shaped light, puts out 40 lux for 5 hours or 10 lux for about 20 hours. So the Lightster, contrasted with the Ixon, either provides half the lux for twice the length of time as the Ixon high beam, or twice the lux for half the length of time as the Ixon low beam. But the Ixon also costs well over $100 - enough to buy almost 3 Lightsters!
I decided to test the Lightster against the Planet Bike Blaze 2 Watt in an under $100 light comparison. The Blaze is a Cree LED commuter light that retails for about $60 dollars. I have used it on overnight rides and it is an acceptable "to see" light for unlit paved roads with no major downhills. For commuting, it is way more than adequate. If the Lightster can hold its own against the Blaze, it's a light worth consideration.