Well, well, well.
I certainly didn't expect this thread to generate the level of debate and controversy that it has, but it now contains some very interesting views and observations!
In the end it's all down to personal preferance I guess, all I, or anyone else can really do is to state what they find effective and in that vein my opinions are these:
1) Working lights are a legal requirement on cycles when ridden on public highways after lighting up time. So fit some and use them, if you don't you are both a moron and illegal.
2) You should allow for points of failure - fit at least two front and two rear lights
3) The lights you do use should be of adequate brightness, I've seen more than a few that are next to useless.
4) Hi-Vis gear is very useful in conditions of poor visibility during daylight / twilight
5) Reflective gear is very useful after dark, especially when worn on the upper body and the ankles
6) Flashing front and rear daylight running lights are good.
The first three points, IMO are non-negotiable.
Points 4, 5 and 6 are purely based on my observations as a driver as to what I find makes a cyclist most visible to me and helps me to see a cyclist in adequate time for me to give him or her the margin of comfort and safety that they deserve. Others will have different opinions no doubt, but this is what works for me.
As a general additional point, I really wish that plod would take more action on all forms of anti-social road use. I know that resources are limited but demonstrating a zero-tolerance approach over the little things would, I think, go a long way towards changing peoples attitudes. I think it would do no harm at all for the police to set up "road blocks" on a random basis , stopping all vehicles that are obviously not in conformance with construction and use regulations; vehicle lights not working or malfunctioning, using foglights inappropriately, chavvy blue front auxilliary lights, cyclists with no lights at night, etc.... Have a "no excuses" policy - issue tickets in all cases and, where the fault makes the vehicle unfit for use, impound it until fixed and that includes cycles.