First off, I'd HIGHLY recommend a reflective vest. This one from Harbor Freight is what I ride with, and I've tested it and found it to be QUITE bright. Excellent performance for $5

I am a big fan of my MagicShine light WITH the taillight also. The taillight is $30 from GeoMan, and comes with a Y adapter. You'll never get another taillight that's nearly that bright for $30, so if you go with their headlight then adding the taillight and running both from the same battery makes a lot of sense.

I have an aftermarket battery, though I never had any trouble with the original and I'd have no problem going with it again.

My only caveat is that the connectors are difficult to pull apart, and you MUST be careful to ONLY pull by the connector, not at all by the wire. I actually bought spare Y adapters and extension cables from DealExtreme for really cheap, because even when being careful I wind up messing up a wire about every 6 months and having to replace it, but since they're about $3 each at DX, I don't much care.

If you want an alternative, here's my recommendation:

I use a P7 flashlight as a backup, but apparently this flashlight is reported to be quite good. Add this handlebar mount this charger and this pair of batteries and you have a very bright and versatile light that you can also use off the bike for $36. These are just the parts that I have and they work for me, there are other options. This will give you a 90+ minute runtime per cell.

For on the back, I'd go with a Pacific Design Works Danger Zone or Radbot taillight for about $30. But IMO it's worth having two lights on the back because you won't be able to tell if one fails. As long as you're ordering from DealExtreme, this taillight is essentially equivalent to the Planet Bike Superflash and sells for $3.50. I put one on my helmet as a backup.