I can think of at least 4 things, some big, some
small, where post-V7
Research Unix was influential
Besides streams, file system switch, /proc, and /dev/fd. v8 had the
Blit. Though Rob's relevant patent evoked disgruntled rumblings from
MIT that window systems were old hat, the Blit pioneered multiple
windows as we know them today. On the contemporary Lisp Machine, for
example, active computation happened in only one window at a time.
V8 also had Peter Weinberger's Remote File System. Unlike NFS, RFS
mapped UIDS, thus allowing files to be shared among computers in
different jurisdictions with different UID lists. Unfortunately, RFS
went the way of Reiser paging.
And then there was Norman Wilson, who polished the kernel and
administrative tools. All kinds of things became smaller and
cleaner--an inimitable accomplishment
No clue what was new in V10
This suggests I should put on my to-do list an update of the Research
Unix Reader's combined table of man-page contents, which covers only
v1-v9. I think it's fair to say, though, that nothing introduced in
v10 was as influential as the features mentioned above.
Doug