1UP has uploaded nearly four minutes of footage from a demonstration that Eidos Montreal gave of Deus Ex: Human Revolution running on a three-monitor Eyefinity setup using an AMD Radeon HD 6870 video card. Not only does the video make a compelling argument for investing in two more monitors, but it also shows off how smooth the PC version is running - despite being several months from release.
Unfortunately, we don't get a look at the UI, but it's likely that they haven't finalized it yet anyway.