A Bargain at $59, I'm hesitant at $75. There's just no way this thing can cost more than $10 to make in the 3rd world, and the USB charging port is now micro-USB and problematic.
1. The lens, which spreads the light out horizontally, is an important advance in safety, and one I suggested 2yrs ago on my blog. According to the DOT, several cyclists have been hit when motorists lost sight of them when getting close enough to pass the edge of the narrow cone of light typical of cyclists taillights. Looking right to find them, they steered in the direction they were looking, and hit the cyclist.
The type of lens used on this light is available here on Amazon Wide Angle Lens for MagicShine, Gemini, and many other Bike Lights / Headlight. Includes O-Ring
for headlights, and I purchased one and loved it 3 years ago now. This feature is especially important for taillights mounted on the back of your helmet, because otherwise when you turn your head, from the motorist's point of view, you disappear.
2. The very versatile and simple mounting system that will wrap around ANY seatpost.
3. It's own internal LION battery offering the best power-to-weight ratio.
2. Weak micro-USB connection
3. The mounting system doesn't work well on the back of helmets, and is too heavy for that application, causing neck strain.
It might have been better to have one of the LEDs drive a narrow beam with it's own flash pattern setting so the light would comprise both a 180 degree spread set to constant-on, AND a very bright narrow flashing pattern to grab motorists attention from long range. (Google "G.I.T. Lit pedaling zen")
(G.I.T. is for GRAB attention. IDENTIFY as cyclist. TRACK cyclist)
That said, I also think it prudent to have at least 2 lights on the back of a bike.
First, it's very important with LION powered lights that you have a fail-over light. Since one light should be set to constant-on, and one to flashing, the flashing one lasting longer makes a natural fail-over. This is true because LION powered devices have to have protection circuits which prevent voltages from going too low. This means, unlike NiMh batteries, which just get dimmer and dimmer, LION powered lights will shut themselves off, and there's no turning them back on until they're charged.
Second, it's important to have lights mounted some distance apart, such as on the back of the seat bag and on the seat post/tube, as that separation helps motorists discern distance and thereby, rate of closure. Motorists have a pretty good idea how far apart those mounting points are, so they can judge their distance from you fairly accurately. They judge vertical separation from behind, and horizontal and vertical from the side.
The logical conclusion is you need 2 lights. This one should be the close-in beacon set to constant on tasked to allow motorists to easily TRACK you, while this Serfas Superbright Usb Taillight (Red, One)
one should be your long-range strobe meant to GRAB motorists attention, telling them you're somewhere up ahead and they may want to change lanes, slow down, or just move over a few feet before they get much closer.
As I currently have two of the Serfas 60's (and a whole box full of PlanetBike lights) I'll wait for the price to come down on this, and see how the USB port shapes up before taking the plunge.