I'd like to think the "everything is a file" mentality would've been taken a touch farther, and the command line tools would deal with networked resources better (eg cp ssh://example.com/~/somefile ~/localcopy)
I would have mentioned it, but I was speaking as if Unix were invented today. Plan 9 is an almost textbook second-system effect; it seems like you have to have invented a Unix first before even starting on something like Plan 9.
