I remember an interview with one of the ex-Plan9 people now at Google (Rob Pike maybe?) talking about how he's switched to Linux, since that's what Google runs on, and finds it a strange experience, as if a bunch of bugs you thought you'd fixed 20 years ago have resurfaced in the main branch. But Linux does seem to be picking up a steady number of the features.
The ideas were good, but somehow they had to take the long way around. It was way ahead of its time.