I have an early 2013 15-inch retina Macbook Pro running the latest stable version of Yosemite on which I've encountered the fabled GPU hang-ups, detailed in this question. I'm almost certain I have the same issue as described; I see similar messages on the console, and it seems to only happen when I open an intensive app like photoshop, thus causing the computer to switch between graphics devices.
In the way of possible fixes, I understand that one can disable graphics switching, but that decreases battery life, which I'd like to avoid. However, I haven't seen the issue in a few weeks anyway, which makes me wonder if it hasn't been fixed. The app store doesn't show any major system updates in the past 30 days. Was there an update I didn't notice that fixed this issue?