Gestures: The basic finger gestures are exactly what you would expect. A one-finger tap-and-hold clips content, one-finger flicks scroll vertically and turn pages. Two-finger gestures open and close apps: Up or down opens an app, while a swipe offscreen closes it. Flicking toward the other screen with two fingers slides it across. Pinches come into play, for zooming out from the Journal to the Library. These gestures can and probably will change to some degree, possibly incorporating more fingers.
Smart Agenda: The sum total of content in the Courier is called the Infinite Journal, but of course there are different ways to view that. "If Pagestream was a novel, Smart Agenda would be your Cliff Notes." That's how the Smart Agenda is described—it summarizes the flowing Pagestream view into an easier-to-manage block of appointments, emails, to-dos, weather and messages from friends. It appears to be the closest thing to a "home screen" found in Courier.
Journal Overview: Here's a more sprawled out view of the journal, highlighting the ability to create a custom cover and more details about search: Besides time, location, file name and tags, it suggests search also works via handwriting recognition (which would be key to making Courier actually work).
The Cloud: The "cloud" is mentioned throughout documents about Courier. Here, we see some of what the cloud means for Courier: Collaborators can leave comments on shared portions of your journal that will show up instantly, with a notification appearing in the Smart Agenda. More importantly, you can "access your journal from any web browser" to make changes, suggesting true fluffy cloud connectivity.
The Browser: Courier's browser looks straightforward, though it uses an index-card metaphor to flip through your history, like a vertical version of Cover Flow. What makes it special is the power to easily clip content, like photos, to keep it in your journal.
Clip, Tuck, Paste: Perhaps the most interesting interface element of Courier—aside from the pen—is clip, tuck and paste. A lot is made of the ability to clip virtually any content, which is "tucked" into the spine to move it from one page or section of Courier to another.
Infinite Journal: The Infinite Journal, as we mentioned, is the heart of Courier. It's an endless notebook for writing, drawing, storing content like a scrapbook and sharing notes with other people. It's paginated, and every item is tagged with a timestamp and geotag. You can also tag pages, for easy searching.
The Pen: The Courier pen is not a dumb stylus: There are two buttons, an eraser, and a twisting mechanism to switch to a different drawing mode. The top button is an undo button, so you won't have to flip it to erase something every time you screw up.
The Front Button: The front button acts as a quick-select. In sketch mode, it lets you jump between pens without having to take the time to switch grips and twist. A full color palette makes us think MS Paint: The Next Generation.
The Camera: Taking a picture with Courier sounds awkward, at least at a skate park. Taking pictures of magazines next to you is probably easier. The crop is adjusted in the viewfinder before the shot is snapped, which happens with a screen tap. There's a dedicated hardware button, which is handy.
The Library: The Library is the Courier's main file browser. It is where everything is organized and cataloged, from journals, photos and applications to "books and subscriptions," suggesting that Microsoft is looking at Courier as a reading device as well.