So, does that mean that the other button could be a middle-mouse click?
Also... do you know if there is pen tilt sensitivity? Can you vary lines based on the angle you're holding the pen?
The middle mouse click I'm not too sure about unfortunately. I do know that the other button on the pen had a function that was similar to a "cut and copy". Could it be configured to allow a middle-click? I would almost think so. The buttons do have settings within the Bluetooth Dives that can be manipulated. I do know for some people that middle-click is crucial.
As for the tilt-sensitivity, I'm not going to say I'm 100% sure on that. With my use it "seems" to have that sensitivity, but remember I'm no artist or a person who is even looking or registering such a level of pen input. My use on the device is strictly from a note taking and quick doodle perspective. I do know that from the previous iterations of the Surface Pen it has a lot better feedback and sensitivity in those areas. That could lead it to have more areas of sensitivity I haven't explored.