We just bought one of the cheap ones from Kmart that has dual screens. It works pretty well. Only prob is ours didn't get much use as one of the kiddies gets sick from watching dvds whilst we're driving.
I purchased a cheap one (Soniq) from JB Hi Fi many many years ago - and it was DOA. Swapped it over for a Phillips that hasn't missed a beat - and it has had plenty of use over the years (not just in the car, but holiday accom. and for kids sleep overs).
Mate purchased a Sony recently, and obvioulsy the screen res and features have improved... he was very happy with it.