I am beginning to get a little fed up with these actioncams claiming to be HD. I have a HD tv and a Sony HD video camera, so I know what HD should look like. This doesn't provide HD quality. It may produce HD size, i.e. 720p, but it does not produce HD quality images.
But aside from that, this seems to be the best of the bunch. It is worth paying a bit more as you get the waterproof feature and the laser for correct positioning. It also has a remote control which will allow you to start or stop recording and also turn the laser on. The laser will only stay on as long as you keep the button depressed, but I can't wait for the first night of fog.
It isn't advertised, but this has a 5 min recording period. So every 5 mins the file is written to the SD card so it won't be lost in case you take the battery out without realising it is still recording. Don't think it will stop after 5 mins, it just writes to the card in continuous 5 min chunks.
To give you an idea of what to expect, the 16GB SD card I used will record 5 hours and 20 mins. I have not tested the battery life yet, but it does charge from a mini usb cable, so this could be plugged into a car charger if needed.
The sound is nothing to get excited over. It does pick up some noise from inside the car, but not much. Have not tried on my helmet when I go racing yet.
All in all I would recommend this. I only gave 4 stars due to the lower than expected picture quality.