When my old Dinotte rear light finally gave up the ghost, I ended up buying a couple of the cheap Phaart lights off Planet X to get me through last winter. Had the Phaart Booster 0.5 Watt on the seat post and the Phaart Bleep Dual 0.5 Watt on the hydration pack. They seemed pretty good for the money, £3 each and ideal for the on-off road riding I was doing at the time. If I was commuting again though, I'd want one of those ones that pulse a steady light.

I have a Bontrager Flare R which I bought based on good reviews. It has four settings, daylight constant and flashing and dark constant and flashing. The daylight settings are super bright while the dark settings are less bright. I like it a lot. I use it on constant/dark setting at night in conjunction with another light in flashing mode. During the day I use it in daylight flashing mode.

Another exposure user, however, with both my white & red lights, the batteries are crack are retaining charge! OK if you fully charge them immediately prior to riding, but useless if they have been charged more than a week before. My old Ay-Up lights have been amazing in this respect, holding approx 90% of their charge for 6 months in storage.

Whatever I use as my primary rear light, I supplement with a small light attached to the back of my helmet. And as much reflective bits as I can muster - invested in a big roll of 3m tape which goes on anything it will stick to. Ankle band, and vest too, if not wearing a backpack.

I actually feel safer riding late at night when traffic is much reduced, although levels of alertness in drivers might be dulled!