Using an r9 280x, I'm getting around 8631 kh/s . I have to say that although the gpu usage is 99% it doesn't seems to stress the gpu as much as dogecoin mining for example. The card stays at a cool 62c using a fan speed of 42% (Sapphire).
The scrypt miners are WAY more optimized to use all GPU resources. This is a very first version that has LOTS of room for improvement (for example, use proprietary AMD instruction set when it applies, and use vector variables).
Oh, and most scrypt miners force overclock, while this miner does not (you need to overclock your GPU manually if you want to increase speed).