Just because you can run it over the network doesn't mean you have to. Like, yeah, you can run Linux with root on NFS and yes it can make you vulnerable to latency problems, but you can also run Plan 9 completely on a single machine with all the myriad filesystems coming from from the local system (mostly virtual, but some actually hitting disk).

If you mean that microkernels ping-ponging between kernel and user space can impact perf: Maybe? I'd really want to see benchmarks.