Many thanks for that, Alexander.
I wish I had that a month ago, because I have just gone through the process of making my application dpi-aware. It's been a bit of a minefield.
Generally the dialogs are ok and the virtualization results would have been acceptable. Where virtualization is not acceptable is where you are doing direct CAD-style drawing on the form's Canvas. The result is that crisp 1-pixel lines become smudged and the whole thing looks awful, completely destroying the advantage of having a high-resolution display. Unfortunately there doesn't seem to be any way of separating the two -- I would have been happy to leave virtualization for the controls if I could be sure of pixel-perfect line drawing on the Canvas.
In the event I have had to do the whole thing. Which has meant going through several dozen forms, making minor tweaks to font sizes and label dimensions on hundreds of controls, and testing everything at 4 different scaling settings. Fortunately I developed the whole thing at 120dpi in the first place, so the adjustments have not been as drastic as they might have been.
But finally it is looking good on my Surface Pro 3 (the arrival of which prompted all this). I have drawn the line at doing multi-monitor scaling because life is too short to do everything.