As for the bad stuff, the low screen resolution gives edges a hint of softness that a higher-res screen would no doubt have solved. It's hard to make out detail on long shots of people and objects, and because you can make out the grid-like structure of the panel, edges and diagonal lines also seem jagged. It's not helped by the use of composite video rather than higher-quality S-video either. But as mentioned, these faults only become a problem when you look more closely at the screen than you normally would - for casual viewing from a normal distance the images are perfectly enjoyable.
With regard to audio, the screen's speakers make dialogue sound clear enough to be heard over the hum of the engine, but sadly they also make Spider-Man 2's high-octane action scenes sound tinny and compressed with no bass whatsoever, and when turned up loud they can get a bit fatiguing on the ears, so it's worth investing in some good headphones. And if you do, you'll be treated to some superb CD and MP3 playback, with the healthy bass and treble levels lending music lots of punch and detail.
If you're thinking of investing in a portable DVD player for those long summer car journeys then the PET712 is a splendid proposition. Not only do the dual screens make it very convenient if you have two kids in the car, but it's also simple to use and looks attractive. It might not deliver the sharpest or most detailed pictures possible, but considering the target audience that's not a big deal - in all other respects it's a very likeable player that should ensure that you'll never have to hear ‘are we there yet?' ever again.