Do you guys think it's better to have one 1watt rear light or have two or three 1/2 watt lights? I currently have a Mars 3.0 and Viewpoint Ultra (Superflash knockoff) and am thinking about getting another 1/2 watt rear light.
I'd go for the redundancy on the rear. As a matter of fact, I do have three blinkies. Batteries seem to run down at different rates, so when one's weak, the others will keep me lit. Having multiple lights also makes it quite clear when one's getting weak batteries.