Thanks, I viewed the downloaded image files on various metro & desktop photo apps. Also minor differences here and there, but never a smooth gradation on my SP2.
I did get the noticeably best result on my SP2 (such as it is) from Photoshop CC. Other apps were a bit worse to one degree or another. For example the Windows 8.1 Photos app showed perhaps the worst brown background dithering on that SmugMug test image.
To be clear, our SP2's don't look nearly as bad as your original unit. But they don't look as continuous tone as my desktop monitor or jnjroach's stock SP2 result...