I have the "mate" model (no wifi). Wifi is probably a wiser choice - to better orient the cam and to setup.
Very good detail corner to corner. But overexposes in bright light and in contrasty scenes (exposes for the shadows not the highlights). Shutter speed is good on a bright sunny day, enough to read plates off slow-ish oncoming traffic as they go past on a 2-lane road (maybe up to about 30mph). But add even a bit of clouds or higher speeds - they get smeared. In this regards in comparison, this is better than mini 806 and 801 dashcams that smear more due to motion. Worse than DOD LS300W, which does not smear license plates even in heavy dark overcast conditions and on traffic coming at me at 70mph (and me driving at 70, so combined 140mph). The Bullet will smear plates of oncoming traffic at these speeds even on a bright sunny day.
As others mentioned, the mini HDMI cable is very stiff and thick. Sturdy but hard to route.
I use my cam with a small $4.99 rated 2A USB adapter in the cigarette lighter socket - no issues.
Footage is shaky, but less than I expected. Nothing like the uncanny digital stabilization of the latest Sony RX cams bit OK for smooth roads (see here for samples of the Sony:
http://www.dpreview.com/reviews/sony-cybershot-dsc-rx100-iv/9). Have not compared to GoPro for that, but resolution and detail seem comparable at full HD, with the GoPro having better exposure.
I would not trust neither the lens nor the control module to be truly waterproof like a GoPro in its case is. But for light rain I would not worry. If someone lends me their Bullet, I am willing to test on my kayak, but would not risk my own - the cable connections and SD card slot cover are where it will likely leak of submerged and subject to vibrations.
Sample footage here (the original looks much better, and free of the compression artifacts from YouTube):
Also note, the above is shot from behind my windscreen, so some extreme corner distortion may be present due to the screen, not the camera. Same with the flare - mostly due to the screen, but there is no provision for a polarizer to cut down on reflections (like there is on the mini 806).
Have not found a better bike cam and service from Pier28 jas been great! Happy with mine.