I like my lights independent; I'm highly unlikely to have dead batteries in everything at once.

Bell Radian set always on the bike: enough to get by with if I'm caught out in the dark unexpectedly. No bombing hills and I'd be a bit nervous on the highway, but for back roads and side streets, I'm tons more visible than the ninjas.
Magicshine clone: I only put this one on if I'm planning to ride for a while in the dark and/or planning to take a major road for some distance.
RadBot 1000: mostly "stored" in its little bracket on the stay, so unless I've taken it for a walk and forgotten to put it back, it's on it's most obnoxious setting backing up the steady setting of the Radian taillight.
Cheapo rubber block flashlight holder: Holds most AA flashlights. I've got a couple of good ones in the 100+ lumen range, so this is the backup for the Magicshine when I'm using it, or a steady "see" light when I want to use the Radian headlight on blink for "be seen."
Helmet mounted headlamp: 3 settings. The lowest is enough to read the unlighted computer, the others are good for roadside repairs or the occasional "point it at the guy who's about to left hook." Chief advantage is having a handsfree light with me when I'm off the bike.

Of course, I use a ton of reflectives too, including retroreflective shoelaces, so I'm definitely taking a belt-and-suspenders approach to being visible at night.