The "lotus" style keyboard (as in the flower, not the software company) has users tilt an analog stick in one of eight directions to highlight a cluster of letters, then hit a colored button to specify the letter. It's a weird-looking solution to the problem of on-screen typing, but a Valve staffer told Kotaku that when people try it, "they're almost instantly faster than [when using] QWERTY."
Big Picture also includes a web browser, which can be used simultaneously with a game through a multitasking feature. You can switch back and forth, Kotaku reports, without going back to your PC's desktop.
This isn't necessarily a first step toward the legendary "Steam Box" console. "What we really want is to ship [Big Picture mode] and then learn," Big Picture Mode team leader Greg Coomer said. "So we want to find out what people value about that. How they make use of it. When they make use of it. Whether it's even a good idea for the broadest set of customers or not. And then decide what to do next."
Update: A trailer for Big Picture Mode, above, shows the keyboard in motion, along with other features.
Update 2: Steam users can now opt in to the beta for Big Picture Mode! Go into settings, select "Steam Beta Update" and restart the Steam client. Once you've completed that, you'll see the Big Picture button in the top right-hand corner.