Have had this unit installed for 2 years now and have zero complaints. I have four kids who stay entertained for hours on long road trips with this. The only difficulty I have had is with loading discs while on the road - not something you want to attempt at 70MPH from the front seat and not something you want the kids unbuckling to do. The IR signal comes in strong for the third row, so the FM modulator (built in) does not get used often. The remote is a little complicated for younger ones (unless they can read), but this is trivial. There is a convenient Pause/Play button on the back that is easily accessed from the front seat.
We have also used this with a Wii and Playstation for tailgating and on the road (vehicle has a 120v AC outlet) - the external Aux In jacks are great for external devices and easily accessed, just don't mind the cables hanging from the ceiling.
The screen does obstruct your rear view, but obviously expected with a large display. The picture is crisp and clear and does not wash out too bad from viewing off-angle (tinted windows help). No complaints from the kids=no complaints from me!
If you are not comfortable pulling your headliner and trim, and attaching things to the structure of your vehicle, professional installation is highly recommended.