In PS 6 an eraser set at 0% hardness (using a round brush) made a smooth transition from center to edge. Now in PS CC it transitions abruptly at a point near the edge and then goes to a pale grey fade. Why is that? And it's only doing so in dark areeas. Medium and light tones erase smoothly. Attached are samples of my trying to make it work. This is a transparent layer with the background not visible (all white instead of the standard checkerboard). I should explain the "L" shaped erased part is two brush edges: hard, left; soft, right.
There have been a number of reports of the GPU-based transparency compositing (over a transparent background) looking a bit funky in Photoshop CC 14.0.
Adobe knows about it and is, I'm sure, striving to fix it in a future update.
A workaround for now is to add solid color layer underneath, or if it's critical you be able to see transparency I believe you can set your Advanced GPU Drawing Mode to Basic to get around that odd look. That preference can be found in Photoshop - Preferences - Performance, [Advanced Settings...] button.
That was it! The weird crunchy edge didn't seem to stay when the layer below was switched back on - so I was able to keep working without having a panic melt-down... But it's nice to see it behave normally again.