My big thing was that the AMD drivers support all of the Linux kernel graphics features. Things like DRM (direct rendering manager) and KMS. One of the neat things about the former is allowing interprocess graphics buffer sharing. One example of where they're super useful is in all of the browsers that run their rendering process separate of their window process. Chrome and Firefox for example. You can just send a handle to the graphics buffer across a unix socket rather than having to use something like Angle (Chrome) and actually send the graphics commands across some IPC mechanism.

this is also one of the mechanisms that Wayland is built on top of.