There are numerous accounts of the graphical glitch issue. It only happens on the background layer, and its happening on a machine with integrated graphics, not

There are numerous accounts of the graphical glitch issue. It only happens on the background layer, and its happening on a machine with integrated graphics, not one of the machines with well known AMD graphics issues. The type of artifact is very similar to texture memory being overwritten. It could very well be a hardware issue, but since it only happens at the login screen and it consistently happens only after the Yosemite update, I'm fairly certain its software.