Space demo. I know people are going to hate me but space is not a good theme for tech demos. Nature, cities, animals and humans, that's where you need the most grunt to present it realistically.
Nature with it's dynamic elements like trees, bushes and grass that moves in the wind, clouds, fog, water, these things are still the most difficult to render.
Cities with massive amounts of vehicles and humans presented on a mass scale and connected with everything from nature. Animals and humans, because fur, hair, skin and clothing is still the most difficult thing to render realistically.
Space? It's EMPTY! You can render some lens flares, stack tons of space ship, make a planet and that's it. There are no real challenges to the rendering pipeline. Even when you try to focus it on a very specific thing like the Appollo 11 demo from NVIDIA, it's still all static and dull.
Unigine Valley impressed me because it has the nature. And it looked absolutely amazing, especially when a storm is dropped intot he scene and everything starts moving. Same reason I dropped my jaw back in 2001 when I've first seen 3DMark 2001 on a GeForce 3 rendering natue scene with first ever pixel shaders. It was so mindblowingly nice for that time I still run that 3DMark almost every time I change a graphic card, just for the sake of good old times. Or the water using DX7 in the end of 3DMark2000. I've NEVER seen such amazing dynamic water done without ANY pixels haders. My mind was blown away.
So, guys at Unigine, stick with that instead. I'll run the demo anyway, but even without seeing it, I already know it won't impress me as much as anything else would...