Responding to pjmlp, a cool project I saw recently that's related to the ones you mentioned is Unikernels [1]. They noticed that a challenge faced by a lot of those projects is hardware support--each OS has to ship with a huge set of drivers to be widely usable. They sidestep this by targeting a VM, which exposes a single hardware interface no matter what it's running on.

[1]: http://anil.recoil.org/papers/2013-asplos-mirage.pdf