I've used Kumho tyres, and found them to be absolutely fine - it's a decent mid-range brand from a company with motor-racing interests.
It's a bit more complicated too than just sweeping statement 'Chinese' tyre - perhaps I should have said tyres with an essentially unknown Chinese brand; the 'ditchfinder' tyres. There are some of the premium brand manufacturers with plants in China, and they turn out top-end tyres, using the same formulations and manufacturing process as in Europe. They just pay the workforce ten-bob and a conker, and it brings the price per unit right down.