I've got several pieces of Polywood on my patio, currently buried under snow.
They really do hold up well (three years outdoors and still look like new), and several people have been fooled into thinking they are painted wood rather than synthetic. The material has just enough flex that the chairs are comfortable to sit on without a cushion.
The only real downside is these are heavy, even heavier than solid wood. That's why they're still out on the patio.