The magnetic Pitan is a fantastic compromise of convenience and security. Despite how it looks and feels, it is surprisingly stable and strong. When the pen is attached to the magnetic tray, it rolls a bit and can slide up and down the length of the tray a few millimeters, but shaking the tray or notebook while the pen is attached isn't enough force to jostle the pen free of the magnets. I was apprehensive at first, but after more and more ridiculous shake and sling tests, I'm really happy and impressed with how well the magnetic tray holds the pen in place.
Where the strength of the magnets fails, though, is if another object forces the pen off the tray or rolls it away from the notebook. This isn't a big deal when the notebook/pen combo is on its own, but it becomes a problem when it's thrown into a collection of other objects, like a bag. The pen still manages to stay attached longer than I would expect, but it will likely get forced off the tray if there's enough motion inside the bag.