So on a trip a few days ago, I stopped to compare my car's taillights to the Ultrafire, which I compared to the Superflash here. The battery in the Ultrafire was charged a few days beforehand, and probably had up to an hour's use before the shoot.
Visually, the outdoor scene was slightly darker than it appears in the shooting, but I didn't want to keep fiddling with the exposure, and this was close enough. Shots were on manual at F2.8 with a 1/2 sec exposure time and ISO 400. I could have taken clearer shots, but also wanted to do this quickly, so made some compromises. The cars in the far background were approximately 80 feet away. Pictures were downscaled to 800x600 for posting here.
Baseline. No lights.
Car taillights on (brake pressed), Ultrafire off.
Ultrafire on, car taillights off.
Both Ultrafire and car taillights on.
In conclusion, the Ultrafire was much visually brighter than the car lights, both in terms of illuminating cars and objects at a distance and the ground up close. I didn't expect it to do nearly this well in comparison, and was very impressed.