I just went and read the wiki page to try and evaluate your statement, but I still don't get it. I mean, I like the distributing computing concept, but what makes Plan 9 especially interesting?
To open a TCP connection, you use the dial(3) function, which basically does the following: write "tcp!name!port" to /net/cs and read out "1.2.3.4!80" (/net/cs resolves the name), then you write "connect 1.2.3.4" to /net/tcp/clone and read out a connection ID, and open /net/tcp/:id/data which is now a full-duplex TCP stream.
There's this emphasis on simple, sane ways of fulfilling tasks on plan9 that permeates the whole system. It's beautiful.
I mean, consider something like vim. It's a nice program, well designed - but undoubtedly insane, just because it's supposed to work in every imaginable context.
It strikes me that plan9 wouldn't be immune to the same phenomenon.
However, if the system permits arbitrary applications to be executed (which plan9 does), then it cannot be shielded from madness. Proof: plan9 has a POSIX compatibility layer (APE), a vt100 terminal emulator and a vim port. It even has an aging full-on linux emulator. I think it could run a really old version of Firefox, but the memory is vague. People swear by Mothra these days anyway.
In any case the C APIs are the same as Plan 9 anyway.