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I have only seen BeOS crash rarely. Any futuristic system needs to be responsive to the user and a great system to program for, which is why Haiku is so exciting.
For a good overview of modern OS research, TUNES' wiki has a good page on this:
http://tunes.org/wiki/index.html
I've been following the CapROS project for a few years too. It followed up on EROS, the Extremely Reliable Operating System