I was also seeing this, I saw artifacts from the iPad app when I opened the document in Photoshop. Some of them were in the layer mask and some on the actual image.
John, when you link to an issue in Adobe Elements 11, how does that relate to my issue in Adobe Photoshop CC 2014, which doesn't have a HandlerTimeline.Framework , which appears to be the cause of the problem you linked to.
in this thread you linked to, someone says it's "a known issue with Retina screens", so are you also implying that this is a screen issue, or an issue with the Retina model of the MBP? does the Retina screen itself have hardware that would cause this, where the non-Retina screens do not have this problem? how could this be? is there a frame-buffer or something like that *in* the screen? i have had mine replaced a few months after buying the rMBP, due to the burn-in issue, and then again when that screen started to develop bad pixel clusters, so i hope this isn't a hardware-resident issue.
wouldn't this be more consistent with issues within the GPU, maybe caused by over-heating or nVidia driver bugs?
do you have a link to more info?