Sorry for the blurry pics but it was hard to hold the camera still with a low shutter speed.
Here is how I have mine mounted as well as a video of the startup. And yes it turns on/off with the car without any button presses. In the video, I do have to press the button to get out of the warning screen though. You only have to do this a few times at first. I just flashed mine with new firmware today so it reset everything. Normally it just goes right to the last screen displayed when it was last turned off.
You can display anywhere from 2 pid's to 7 on the screen at one time. But you can customize 11 or 12 different displays and cycle through them with a single button push. You can also change the display color to 16 million different colors (RGB combinations)
My favorite feature is the data logging. I'm not sure if the others gauges do this or not. If not that would be a deal breaker for me. It also has a valet mode where it can record different sensors for maximum values like RPMs or MPH so you can tell if someones been joyriding. I'm going to test this feature out at the dealer when I take my car in for some minor services.
The only thing that I thought was a cool feature on the ScanGuage that isn't on the DashHawk is the trip logger. I think it would be cool to record various parameters over a long road trip. The logging on the DashHawk can only record I believe is about 20-30 mins with the new firmware update. But I could be mistaken.
Another nice thing about it is that is extremely easy to unplug and take in your house and download the data to a PC. No need for a laptop in your car to download the data. And the PC software is top notch. Very easy to use interface and you can edit all your settings from your PC then upload them to the device. Or if you change them on the device, you can download them to the PC in case you mess things up and you want to revert back to a known good profile.
So you can tell that I'm slightly biased towards the DashHawk

but I'm sure the other devices are great too. I just haven't tried them.
[/end endorsement]