I have been burned by *nix hybrids in the past. I had high hopes for the debian BSD project, however actually installing that left me in a pretty unusable state.
Nexenta is currently tempting me, an OpenSolaris/Ubuntu Hybrid with a sun kernel and the ZFS file system, as well as the very usable Gnome interface. It remains in alpha state. The installer is not the ubuntu installer, but instead a text based installer similar to BSD projects. As the sun kernel does not have as much FS support as the linux kernel, your choices are basically ZFS or nothing. Which is not going to make a lot of users happy.
My problem with projects like this is that they don't usually stand a chance of swaying users from each of their component camps. The solaris people are not going to move to Nexenta as there are no man pages (license issues), the GNU people are not going to move due to a lack of apt-get (license issues) and the fact that a majority of GNU people seem to be perfectly content with the highly configurable 2.6 series Linux Kernel.
It remains to be seen when Nexenta moves out of alpha and hits beta status.