The pen is actually two active parts in one. There's the N-Trig stylus part, which is powered by a AAAA battery and sports two side buttons (one for erase, one for right click), as well as the 256 pressure level tip. At the other end, there's a button similar to the clicky button you'd find on a retractable ballpoint. This button is completely separate from the actual drawing part of the pen. It's driven by a pair of coin cells and connects to the Surface Pro 3 using Bluetooth.
Pressing this button fires up the Metro version of OneNote. If Metro OneNote is running in the foreground already, it creates a new note. If the device is locked, it starts Metro OneNote in a special locked-down mode that lets you write things down but does not allow access to saved notes, the file system, or anything else. If the screen is off when the button is pressed, it will come on.
The idea here is simple: whatever you are doing with the Surface Pro 3, you can always, with a single click of the purple pen button, start OneNote to start jotting down ideas.
My pen experience was problematic. The first unit I had seemed to be defective; pressing one of the buttons on the barrel of the pen would almost always result in the tablet losing contact with it. It no longer laid down ink and did not show the on-screen indication of where the tip was, and then the two stopped talking to each other entirely (though the separate, Bluetooth-driven end button continued to work). After a few minutes, the pen would once again be recognized and I could once again use it to draw.
Even when it was working, it seemed temperamental. The system would register as if I were touching the screen even when hovering. This meant that when writing things down, my text would become even more indecipherable than it normally is, as there would be lines joining everything together because the system didn't notice that I was lifting the pen between strokes. This behavior was intermittent, however. Some times it would work exactly as it should, registering that the pen was touching the screen only when it was.
Microsoft sent me a replacement pen (it would normally cost about $50 to buy a new one—another downside of active pens relative to passive ones), and it worked perfectly.
Adobe Photoshop stubbornly refuses to use the Microsoft-provided pen API, instead depending on the Wacom's WinTab API for its pen support. After installing the WinTab driver from N-Trig's website, Photoshop gained basic pen functionality. The pen doesn't include the tilt/orientation support that the high-end Wacom pens support. In this regard, it's no different from the previous Surface Pros, as they didn't appear to have tilt support either. If this is a feature you want in a tablet, you'll have to fork out for one of Wacom's extraordinarily expensive Cintiq devices.
