If you're still a non-believer of Tegra 4 graphics, this demo may surprise you, and it enforces the idea that OUYA should've at least arrived with Tegra 4, if nothing else, considering OUYA will have its public release later than the launch of Tegra 4 on the market. Nvidia showed off that Tegra 4 can enable much more realistic graphics for mobile devices when compared to "non-Tegra 4" (probably referring to Tegra 3).
We've seen the benchmarks for Tegra 4 already, and they look very impressive, both CPU and GPU wise. The quad core Cortex A15 CPU manages to go under 500 ms in Sunspider, and loads virtually any web page in 1 second (as long as it's not limited by your connection speed and other factors). Cortex A15 should remain the fastest CPU core in mobile in 2013, even if others like Qualcomm's S800 manage to have a higher clock speed.
Then there's the GPU, with a power of 75 Gflops, which beats even Apple's own A6X GPU which has 71 Gflops. Considering Nvidia achieved this with only an 80mm2 die size vs A6X's 120 mm2 die size, I'd say that's pretty impressive, even if it's arriving about half a year late in the market. We'll probably still see Apple's A7X (probably not the A7 though) beat Tegra 4's GPU, but if this is actually the performance of the Tegra 4 that is to be used in mobile devices, then it might beat even Adreno 330 and possibly even Samsung's Exynos 5 Octa, which is presumably using PowerVR SGX543 MP3 used in iPhone 5, but at twice the clock speed.
Nvidia still missed their chance to create the "most powerful mobile GPU" this year (again, assuming A7X will beat it), but if they make next year's GPU based on the Maxwell (successor of Kepler) architecture, use a 120mm2 die size just like Apple, and make it at 20nm process, I think they can finally have the most powerful GPU in the market, by a large margin. But that's a big if, as Nvidia tends to not be early adopter of process shrinks, and doesn't seem to want to make larger and more expensive chips either. I do hope they do that though, because it would be the smart thing to do.