Same thing here on an nVidia Quadro card. Basically, once again the logic for anti-aliasing the viewport has been reversed. I have Viewport Anti-Aliasing samples set to 8. While manipulating the viewport, the model is anti-aliased (it should not be so), while not doing anything (let go of mouse), the anti-aliasing disappears. This happened pretty much over night, didn't see that in yesterdays build.
From my side there are no more steps to reproduce it, it was fixed somehow in one of the last 30 commits. Todays build does not have the problem any longer, so this report can be closed as far as I am concerned. I'm not the original reporter though, so maybe ask @Ishaq Al Asyja' (McRavenIND) for confirmation as well.