May be GPUs are a bad example - for USB, FireWire and most of the other driver code and supporting infrastructure that constitutes the Linux kernel, the point (that its design is mostly uninfluenced by older UNIX) still stands. Besides the old UNIX vendors did not seem to have contributed much in terms of Linux GPU stack, maybe because that's not where the money was/is. SGI contributions for e.g. are in the area of FS and scalability predominantly. (I am aware that some places use Linux workstations for Graphics - but Nvidia essentially ships there own Xorg replacement stack along with highly kludgy properietary driver - nothing remotely related to great design there.)

Filesystems, TCP/IP stack, Multi core scalability etc are the areas that most benefited from old UNIX design. (Questionable in case of TCP/IP - Alan Cox rewrote it and I am not sure if he was influenced by any older UNIX implementation or not.)