I have a DOD dashcam and love it. 

Re GPS, as someone else mentioned, they can usually imprint your speed on the video which isn't mentioned in the article. 

Also about the screen, mine can be set to 'screensaver' mode so it shuts off after a minute. Plus, mine is mounted on the other side of the rear view mirror so you cannot see it while driving. 

All in all, would not drive a vehicle without one.