The big drawback is that it's a touch screen overlay of the display screen. The display screen is not easily reached from the driver's seat. The controls for the GPS are accessed through the display overlay. A great portable GPS is available for about $100 which you can take with you for use in rental cars, program in the comfort of your home and have lifetime free map upgrades.
If that's a touch screen it's going to be unusable/dangerous to use since the imid is so far away.
Also, these replacement OEM-fit units tend to use WinCE for its OS which means very slow loading times, rendering the rear camera useless since you got to sit and wait for it to boot up anywhere from 30 seconds to a minute before anything shows up on the screen. That's usually the main dealbreaker for these third party units in my experience.