It's less of a driver and more of an operating system. Basically self-contained with all the support libraries it needs. Super easy to port to a new operating system and any driver improvement work on all OSes.

But the approach also has many downsides. It's big. It ignores all the native stuff (like linux's GEM interface).

It also has random issues with locking up the entire system. Like if you are debugging a process with the linux drivers, a breakpoint or a pause in the wrong place can deadlock the system.