I love the SunOS kernel. ZFS, Dtrace, Zones all make it desirable. But OpenSolaris is a code repository, not a distribution and you have to go elsewhere if you want a free distro. Nexenta looked the most promising, but then went quiet for a while (at least on their webpage) after shifting their focus to a smaller package set they called Nexenta Core Platform. I was very pleased to see an offer of collaboration from the Debian project leader in their forums and now Nexenta.com has released a new NAS package (not free though) and at the same time Suns “Project Nevada” seems to be bearing fruit after hiring Ian Murdock (the chap who started Debian)
OpenSolaris Developer/Community editions pale in comparision to Ubuntu for range of packages and usability, perhaps Nevada can sort it out. I am hopeful that Nexenta get it together and be the GNU/Solaris distro I really want (see here for some screencasts by Martin Man showing how cool it already is).