I'll get this bit of reassurance out of the way: Infinite runs perfectly. Our demo PCs were admittedly above average: an AMD FX-8120 (an octo-core CPU) and a single card in the AMD Radeon 7900 series (I didn't have time to verify which one), alongside 16GB RAM on Windows 7. With that considered, I didn't experience any hiccups, frame rate dips, no texture pop-in, or crashes.
Digging into the settings menu, here's what was adjustable...
An Irrational developer told me that Infinite is running on DirectX 10, but that it does take advantage of some DX11 features.
Reassuring stuff - if only every dev gave the PC as much love.