This was posted in discussion forum. Since it has been verified as a change in CS6, I will add it to the "Feature Request" forum.
In CS5 I routinely updated a current gradient slider by clicked on an existing gradient slider, then dragged the resulting color swatch from the color or swatch panel, into the gradient panel, to add or update a slider color. It was much faster than option dragging the current slider and deleting the slider I wished to replace. See video for example. Works fine in CS5. No dice in CS6. I hope this little oversite is corrected soon. This is something I cannot live without, really.
To add to this feature request, I'd like to see a button to "srip" out all but the 2 end colors in a gradient. I often want to create a new gradient based on an old one. Manually dragging the sliders out of an existing gradient can be time-consuming.