I run multiple taillights, which I started because I've had my rear light go out on occasion than just for brightness . . . but it does make you more visible. I've also put several cheap CR2032 powered LED lights on my backpack (you can pick 'em up for a couple dollars at the dollar store - I think they make them for putting on pet collars), and I'll turn them on when visibility is poor (snow/rain) and I'm out in the dark. More the merrier.
If you're really concerned about how visible you are, get your wife/husband to ride your bike after dark down the street and see how visible things are from your car. That's how I tested all the lighting and reflective stuff I've got to figure out what made the most sense to use. My observations:
- Reflective stuff on the ankles is better than anywhere else. The movement they generate really draws attention.
- Certain types of reflective stuff work better in different conditions. You'll have to test out a variety to figure what works for the conditions you're cycling in.
- If you're running multiple lights, spread them out. Try to put one high, one low, one right, and one left. Keep your brightest one running solid, and the others flashing. The flashing ones grab attention, but the solid one makes it easier for a driver to gauge distances.
- Unless you have reflective stuff on your gloves, there's no point signalling at night.
- Fluorescent clothing is best at around dusk, but not any better than any bright coloured stuff when it's pitch black.
- Standard bike reflectors are useless compared to modern bike lights. Replace your reflectors with more lights if you have the option.