I just bought an Imac 27. When I use Adobe Illustrator and I zoom in over some vector shapes I noticed that the lines are not too clear, the effect is a bit similar to a raster image. If I click command+Y (outlines preview) and then I click it again the problem is fixed. I uploaded a little video of the issue.
Is this a software problem or it can be my graphic card?
The problem with GPU rendering is that the GPUis fast, but at the cost of precision.
Only thing you can do now is to report this as a bug:
Maybe there are driver updates available, but that's about it.