I got my DiNotte 300R yesterday.
Package contents, minus the packing materials.
The light has a quick-release receptacle that slides over the two-hole swivel tabs and locks into one of the holes. They're US-style reflector brackets, and you can get more of them at your LBS since they're not a proprietary DiNotte item. If you prefer to bolt the light on, remove the quick-release receptacle and you'll find two threaded holes so you can bolt the light on instead.
Runtime/charging info from the instruction sheet
The 300R charging from my computer's USB port
The 300R is bigger than I realized from the photos. The black part is one machined block of aluminum. It feels quite solid and hefty.
Weight comparison to a SuperFlash with NiMH AAAs. The 300R is about 100 grams lighter than my DiNotte 140 with a 2-cell Li-ion battery pack and a minimalist light mount.
Beamshots
To compare lights, right-click the links below and open them in new tabs. Then you can click from one tab to another to compare lights back-to-back.
Planet Bike BRT5
NiteRider Cherry Bomb
Planet Bike SuperFlash
PDW Radbot 1000
DiNotte 140 on LOW
DiNotte 140 on HIGH
DiNotte 300R on HIGH. It's not your imagination, the 300R has
lower intensity than the 140, because the beam is more diffused.
Nova BULL powered by a DiNotte Li-ion battery pack. This is a weatherproof emergency-vehicle mini-strobe, about 120 lumens for the red model, and runs well on 9.6-15 volts. It's not made for bikes, so mounting it required creativity.
Ultrafire WF-501B flashlight with native red LED (does not have a flash mode). This could be a nice add-on if you routinely ride in very thick fog , but you'd need to aim it precisely since it's such a focused beam.
The photos were taken at f8.0, 3.2 seconds exposure, ISO 50, auto white balance. The lights were running in steady-burn mode to allow general intensity comparisons. Distance to the wall is about 6 meters.
Remarks
With most rechargeable lights, you're advised to unplug the battery pack when storing or packing the light. This prevents the light from accidentally turning on and setting your suitcase on fire ;-) and also prevents the battery from being depleted in long-term storage by lights that have "soft-off," such as DiNottes, instead of a mechanical ON/OFF switch. But since the 300R's battery can't be unplugged, (1) keep it on the charger if you aren't going to use it for a long time; and (2) if you pack the 300R, put it inside something cylindrical like an empty shampoo bottle, to prevent its power button from being bumped or held down.
Day or night, I'd feel confident on fast highways with the 300R, the 140, the Nova, or other lights that have that level of output, as long as they're running a flashing mode. They'd also help ease my mind in fog, heavy snow, heavy rain, or heavy glare (riding towards the rising or setting sun). If you want a high-output taillight like this, but $200 is too much, consider the Magicshine or the AA-powered DiNotte 140.
If properly aimed, even a smaller light like a SuperFlash will really help in overcast or twilight conditions, not to mention in darkness. So if you're sticking with your trusty SuperFlash/etc, or keeping it onboard as a secondary light, make sure it's aimed right at the overtaking traffic, because the beam is pretty directional. Make it count.