Well actually, 150% DPI scaling works fine in Window 7, but the same cannot be said for Steam or other programs. I had to use a modded Pixelvision skin with largest fonts to make it even usable in 4K, Steam is not affected by the Windows DPI scaling at all.
Sony Vegas... it does work with DPI scaling, half-assed a bit though. the top tool bar is bonked out, and the words are still tiny.
Yea we're not there yet for resolutions beyond 1440p for most programs.